Nutritional supplements to increase muscle mass.

Although nutritional supplements purported to increase muscle mass are widely available at health food stores, gyms, by mail order, and over the Internet, many of these supplements have little or no data to support their claims. This article reviews the theory and research behind popular nutritional supplements commonly marketed as muscle mass builders. Included are the minerals chromium, vanadyl sulfate, and boron, the steroid hormone dehydroepiandrosterone (DHEA), beta-methyl-hydroxy-beta-methylbutyrate (HMB), creatine, protein supplements, and amino acids. Research has shown that chromium vanadyl sulfate, and boron do not appear to be effective in increasing lean body mass. The few studies examining DHEA have not supported the claim of increased muscle gain. Preliminary work on HMB supports an anticatabolic effect, but only one human study is currently available. Many studies reported increased body mass and several have reported increased lean body mass following creatine ingestion. This weight gain is most likely water retention in muscle but could also be due to some new muscle protein. Although athletes have a greater protein requirement than sedentary individuals, this is easily obtained through the diet, negating the use of protein supplements. Studies on amino acids have not supported their claim to increase growth hormone or insulin secretion. Nutritional supplements can be marketed without FDA approval of safety or effectiveness. Athletes who choose to ingest these supplements should be concerned with unsubstantiated claims, questionable quality control, and safety of long-term use.     

Storage Stability of Antioxidant-Washed Myofibrils From Chicken White and Red Muscle

Oxidation and gel-forming ability of chicken white (breast) and red (leg) muscle myofibrillar proteins during storage at 0°C were examined. Breast myofibril gels exhibited greater shear moduli than leg myofibril gels throughout 8 days storage. Shear moduli of both breast and leg gels in the intermediate temperature zone (45–55°C) decreased during storage, but at >55°C, they either increased or remained unchanged. Lipid oxidation was inhibited by washing myofibrils with antioxidants propyl gal-late, ascorbate, and tripolyphosphate. However, these antioxidants did not affect the content of protein carbonyls, and only slightly decreased the amine content during storage. Storage affected the kinetic process of myofibril gelation independently of antioxidant treatments.     

Post mortemRelease of Fish White Muscle α-Actinin as a Marker of Disorganisation

α-Actinin release and its degradation from myofibrils Z-line were studied in post mortem white dorsal muscle from bass and sea trout stored at 4°C and 10°C. Using α-actinin specific antibodies, we show that this protein is rapidly released within the first 24 h for the two species, and reaches a plateau within 4 days. Proteolysis take place very rapidly in bass muscle yielding 80 and 40 kDa fragments from α-actinin as major bands of proteolysis. Sea trout muscle is more resistant, and muscle stored at 4°C is not significantly α-actinin degraded even 10 days after death. In the case of sea trout muscle stored at 10°C, an increasing quantity of 80 and 40 kDa fragment can be observed after the third day. These results show that release and proteolysis of α-actinin are time- and temperature-dependent processes that take place at the early stages of fish storage. Furthermore, we observed that proteolysis of α-actinin seems to be dependent on fish species. In both species studied, the early release of α-actinin comes before the degradation of released molecules, and appears as a biphasic process throughout the disorganisation of post mortem muscle in fish cold-stored above 0°C.     

Myosin is solubilized in a neutral and low ionic strength solution containing l-histidine

Myosin, one of the major myofibrillar proteins, is insoluble at low and physiological ionic strength and soluble at high ionic strength. In this study, the behavior and morphology of myosin solubilized in a low ionic strength solution containing l-histidine (l-His) was investigated. More than 80% of myosin was solubilized in a low ionic strength solution with dialysis against a solution containing 1 mM KCl and 5 mM l-His. Transmission electron microscopy with rotary shadowing demonstrated that the rod of myosin in a low ionic strength solution containing l-His is longer than that of myosin in a high ionic strength solution. The elongation of the myosin rod in a low ionic strength solution containing l-His would inhibit the formation of a filament, resulting in the solubilization of myosin.     

Effect of hydroxycinnamic acids on lipid oxidation and protein changes as well as water holding capacity in frozen minced horse mackerel white muscle

The antioxidant effectiveness of different hydroxycinnamic acids for inhibiting the formation of off-flavours associated to rancidity in minced frozen horse mackerel white muscle stored at −10 and −18 °C was studied. The influence of lipid oxidation on protein aggregation, protein denaturation and water holding capacity was also determined. Caffeic acid, o-coumaric acid and ferulic acid were the antioxidants tested. The order of antioxidant effectiveness was caffeic acid > ferulic acid > o-coumaric acid accordingly with previous results obtained in chilled horse mackerel. A strong dependence of antioxidant effectiveness to the ratio lipid/antioxidant concentration was observed. There was no evidence to suggest that antioxidants reduce protein aggregation or water holding capacity changes. Protein aggregation was not accompanied by gross protein denaturation, as monitored by differential scanning calorimetry. No evidence was found for a link between extent of lipid oxidation and degree of protein aggregation or water holding capacity changes.     

亲水胶体和玉米变性淀粉对鸡胸肉匀浆物凝胶特性的影响

采用三因素三水平的完全随机试验设计,研究卡拉胶(κ型,κCG)、魔芋胶(KGM)和玉米变性淀粉(MCS)对鸡胸肉匀浆物保水性、硬度及超微结构的影响。结果表明,卡拉胶、魔芋胶对匀浆物凝胶体系的保水性和硬度均有极显著影响(p ＜ 0.01),而玉米变性淀粉对凝胶保水性有极显著影响(p ＜ 0.01),对硬度有显著影响(p ＜ 0.05)。卡拉胶和魔芋胶之间极显著(p ＜ 0.01)的交互作用,魔芋胶和玉米变性淀粉两者之间显著(p ＜ 0.05)的交互作用均都影响着保水性和硬度,而卡拉胶和玉米变性淀粉的交互作用只对保水性有影响。魔芋胶、卡拉胶和肌肉蛋白可以形成三维网状结构,玉米变性淀粉填充到凝胶网络空隙中起着填充剂的作用,这种结构使得凝胶体系具有较好的三维空间结构,从而影响着凝胶体系的保水性和硬度。     

Grape seed proanthocyanidin extracts alleviate oxidative stress and ER stress in skeletal muscle of low‐dose streptozotocin‐ and high‐carbohydrate/high‐fat diet‐induced diabetic rats

Although ER stress in pancreas, liver, and adipose tissue was reported to be a novel event linked to the pathogenesis of type 2 diabetes mellitus, there is much less information on this event in skeletal muscle. Some studies indicated that treatment with antioxidants had beneficial effects on ER stress and diabetes. This study focuses on the effects of a strong antioxidant, grape seed proanthocyanidin extracts (GSPE), on skeletal muscle in diabetic rats induced with low dose streptozotocin‐ and a high‐carbohydrate/high‐fat diet. After 16 wk of GSPE treatment, diabetic rats showed decreased plasma glucose levels and insulin resistance. The efficacious effect of GSPE was manifested by the amelioration of muscular damage and dysfunction, as observed by histological examination and periodic acid Schiff staining. Concurrently, calcium overload and the abnormal activities of antioxidant enzymes and ATPases in diabetic muscles were partially reversed by GSPE treatment. GSPE also increased the activity of protein kinase B (a mediator of insulin's metabolic action) and partially alleviated severe ER stress. These findings suggest that GSPE may have auxiliary therapeutic potential for type 2 diabetes mellitus by decreasing oxidative stress and ER stress in skeletal muscle.     

雅安罐罐肉加工与贮藏过程中肌肉蛋白质的变化

为了探明雅安罐罐肉蛋白质的变化规律,以不同加工与贮藏阶段的罐罐肉为对象,采用常规理化检测方法以及SDS-PAGE电泳法分析其蛋白质的变化情况。结果显示:罐罐肉在油炸结束后蛋白酶活性为零;非蛋白氮(NPN)与游离氨基酸(FAA)含量在油炸结束时显著上升(P<0.01),FAA达到最大值(219.2 mg/100 g),在贮存的前期与中期缓慢下降,后期又有所回升,NPN达到最高值(0.616%);肌浆蛋白和肌原纤维蛋白经过高温油炸,蛋白质含量(干基)下降为4.18 mg/g和4.70 mg/g,大于66ku的蛋白质条带完全消失,积累大量小于16ku的条带,肌浆蛋白贮藏后期还出现了51ku和42ku的新条带。研究结果表明,雅安罐罐肉蛋白质的变化主要发生在油炸阶段,贮藏过程中的变化非常缓慢。