Leucine Transamination Is Lower in Middle-Aged Compared with Younger Adults

Elucidating the Pharmacological Properties of Zingiber officinale Roscoe (Ginger) on Muscle Ageing by Untargeted Metabolomic Profiling of Human Myoblasts

(1) Background: Muscle loss is associated with frailty and a reduction in physical strength and performance, which is caused by increased oxidative stress. Ginger (Zingiber officinale Roscoe) is a potential herb that can be used to reduce the level of oxidative stress. This study aimed to determine the effect of ginger on the expression of metabolites and their metabolic pathways in the myoblast cells to elucidate the mechanism involved and its pharmacological properties in promoting myoblast differentiation. (2) Methods: The myoblast cells were cultured into three stages (young, pre-senescent and senescent). At each stage, the myoblasts were treated with different concentrations of ginger extract. Then, metabolomic analysis was performed using liquid chromatography-tandem mass spectrometry (LCMS/MS). (3) Results: Nine metabolites were decreased in both the pre-senescent and senescent control groups as compared to the young control group. For the young ginger-treated group, 8-shogaol and valine were upregulated, whereas adipic acid and bis (4-ethyl benzylidene) sorbitol were decreased. In the pre-senescent ginger-treated group, the niacinamide was upregulated, while carnitine and creatine were downregulated. Ginger treatment in the senescent group caused a significant upregulation in 8-shogaol, octadecanamide and uracil. (4) Conclusions: Ginger extract has the potential as a pharmacological agent to reduce muscle loss in skeletal muscle by triggering changes in some metabolites and their pathways that could promote muscle regeneration in ageing.

A High-Fiber Diet Decreases Postabsorptive Protein Turnover but Does Not Alter Insulin Sensitivity in Men with Type 1 Diabetes Mellitus

BACKGROUND

High-fiber diets (HFDs) are recommended in the diet of persons with diabetes, yet such diets can impair macronutrient digestion and/or absorption, modify insulin sensitivity, and reset metabolism.

OBJECTIVES

We studied the effects of a HFD on the kinetics of whole-body protein, a macronutrient that could be affected by dietary fiber, in type 1 diabetes mellitus (T1DM), under both basal-low insulinemic and hyperinsulinemic conditions.

METHODS

Eight men with T1DM (body mass index range: 21.8-27.8 kg/m2) were studied twice - before and after the addition of guar gum (∼15 g/d) to their usual diet for ∼4 mo. Whole-body protein degradation (i.e., the rate of appearance [Ra] of endogenous leucine), leucine disposal to protein synthesis (PS), deamination, and reamination, were determined before and after the HFD, both in the postabsorptive state and following a euglycemic, hyperinsulinemic, hyperaminoacidemic clamp, using isotope dilution methods.

RESULTS

After the HFD, mean values (± SEs) for postabsorptive leucine Ra decreased by ∼20%: from 2.52 (0.15) to 2.03 (0.16) μmol x kg-1 x min-1, P < 0.049, after vs. before the HFD respectively. PS also decreased, by ∼25%: from 2.03 (0.15) to 1.57 (0.15), P < 0.045. Leucine concentration (P = 0.1) and reamination (P = 0.095) decreased moderately, whereas deamination was unchanged. Following the clamp, plasma amino acid concentrations (P < 0.001), leucine deamination (+ ∼50%, P < 0.00002), reamination (+ ∼30%, P < 0.0007), and PS (+ ∼35%, P < 0.00001) were all increased compared with postabsorptive state values, whereas endogenous leucine Ra was suppressed (by 15%, P < 0.00001, and by 25%, P < 0.001, with the primary or the reciprocal pool models, respectively). No significant differences in these insulin effects before compared with after the HFD were observed. Metabolic control (glycated hemoglobin), daily insulin requirement, and insulin-mediated glucose disposal were unchanged after the HFD.

CONCLUSIONS

A HFD downregulates postabsorptive protein turnover in men with T1DM, by decreasing both protein degradation and synthesis, possibly due to a subtle decrease and/or delay in amino acid absorption. It does not significantly affect the insulin (and amino acid sensitivity) to protein turnover, glucose disposal, and metabolic control.