Myocardial subcellular glycogen distribution and sarcoplasmic reticulum Ca2+ handling: effects of ischaemia, reperfusion and ischaemic preconditioning

Effect and possible mechanisms of saponins in Chinese herbal medicine exerts for the treatment of myocardial ischemia-reperfusion injury in experimental animal: a systematic review and meta-analysis

Introduction

Preventing ischemia-reperfusion injury is the main direction of myocardial infarction treatment in the convalescent stage. Some studies have suggested that saponins in Traditional Chinese medicine (TCM) preparations can protect the myocardium by various mechanisms. Our meta-analysis aims to evaluate the efficacy of TCM saponins in treating myocardial ischemia-reperfusion injury (MIRI) and to summarize the potential molecular mechanisms further.

Methods

We conducted a literature search in six electronic databases [Web of Science, PubMed, Embase, Cochrane Library, Sinomed, China National Knowledge Infrastructure (CNKI)] until October 2022.

Results

Seventeen eligible studies included 386 animals (254 received saponins and 132 received vehicles). The random effect model is used to calculate the combined effect. The effect size is expressed as the weighted average difference (WMD) and 95% confidence interval (CI). Compared with placebo, saponins preconditioning reduced infarct size after MIRI significantly (WMD: -3.60,95% CI: -4.45 to -2.74, P < 0.01, I2: 84.7%, P < 0.001), and significantly increased EF (WMD: 3.119, 95% CI: 2.165 to 4.082, P < 0.01, I2: 82.9%, P < 0.0 L) and FS (WMD: 3.157, 95% CI: 2.218 to 4.097, P < 0.001, I2: 81.3%, P < 0.001).

Discussion

The results show that the pre-administration of saponins from TCM has a significant protective effect on MIRI in preclinical studies, which provides an application prospect for developing anti-MIRI drugs with high efficiency and low toxicity.

Subcellular localization- and fibre type-dependent utilization of muscle glycogen during heavy resistance exercise in elite power and Olympic weightlifters

AIM

Glycogen particles are found in different subcellular localizations, which are utilized heterogeneously in different fibre types during endurance exercise. Although resistance exercise typically involves only a moderate use of mixed muscle glycogen, the hypothesis of the present study was that high-volume heavy-load resistance exercise would mediate a pattern of substantial glycogen depletion in specific subcellular localizations and fibre types.

METHODS

10 male elite weightlifters performed resistance exercise consisting of four sets of five (4 × 5) repetitions at 75% of 1RM back squats, 4 × 5 at 75% of 1RM deadlifts and 4 × 12 at 65% of 1RM rear foot elevated split squats. Muscle biopsies (vastus lateralis) were obtained before and after the exercise session. The volumetric content of intermyofibrillar (between myofibrils), intramyofibrillar (within myofibrils) and subsarcolemmal glycogen was assessed by transmission electron microscopy.

RESULTS

After exercise, biochemically determined muscle glycogen decreased by 38 (31:45)%. Location-specific glycogen analyses revealed in type 1 fibres a large decrement in intermyofibrillar glycogen, but no or only minor changes in intramyofibrillar or subsarcolemmal glycogen. In type 2 fibres, large decrements in glycogen were observed in all subcellular localizations. Notably, a substantial fraction of the type 2 fibres demonstrated near-depleted levels of intramyofibrillar glycogen after the exercise session.

CONCLUSION

Heavy resistance exercise mediates a substantial utilization of glycogen from all three subcellular localization in type 2 fibres, while mostly taxing intermyofibrillar glycogen stores in type 1 fibres. Thus, a better understanding of the impact of resistance training on myocellular metabolism and performance requires a focus on compartmentalized glycogen utilization.