Malic acid — can ordinary acid from apples give muscles a boost?

Aim of the study: This systematic review and meta-analysis evaluated the efficacy of topical applications, compared to placebo or other treatments, for the management of xerostomia in older adults. The PICO focus question set for this study was, "What is the most effective topical therapy as opposed to systemic or other therapies for the treatment of xerostomia and salivary gland hypofunction, in elderly patients?"

Results: This systematic review concluded that topical applications for the treatment of dry mouth provided symptomatic relief in older adults; however, their role in improving salivary flow rates was inconclusive due to a lack of sufficient evidence.

Aim of the study: Oral graft-versus-host disease (GVHD) is a common complication of hematopoietic stem cell transplantation. This study systematically reviewed Randomized Controlled Trials (RCTs) with the objective to investigate the effectiveness and side effects of topical agents used for the treatment of oral GVHD.

Results: Five RCTs were included in the qualitative synthesis of results. Two RCTs were associated with a certain risk of bias. Budesonide produced the highest overall treatment response. Malic acid, clobetasol, and dexamethasone increased resting salivary flow rates. Curcumin in orabase showed results similar to corticosteroid treatment. Adverse effects were observed in groups receiving budesonide, dexamethasone, clobetasol, and tacrolimus. The most frequent adverse effects were burning sensations, fungal infections, and gastrointestinal disorders, but none were severe. Given the small number of RCTs conducted and the differences between study designs, it is difficult to make direct comparisons. Malic acid appears to be effective for treating xerostomia caused by graft-versus-host disease. Budesonide had the highest overall response rates but was also associated with the greatest number of adverse effects. Further research is needed to confirm these findings.

Aim of the study: Several therapeutic modalities for the prevention of calcium oxalate (CaOx) stones have been studied, but only a select few of these modalities have been incorporated into the American Urological Association guidelines. Our study aimed to organize and interrogate existing research that may be promising for CaOx prevention.

Results: Of the 6155 identified articles, 38 were included in the final analysis. The five distinct categories of interventions for stone prevention were "medications", "herbal supplements", "food and macronutrients", "micronutrients", and "enzymes and probiotics". Modalities found to reduce known urinary risk factors were tolvaptan, cranberry juice, magnesium citrate, the oxalate-degrading enzyme ALLN-177, and malic acid. Preventive treatments that reduced stone formation were sodium-glucose cotransporter-2 inhibitors, eicosapentaenoic acid, and ethane-1-hydroxy-1,1-diphosphonate. Treatments that reduced urinary risk factors and stone formation were Phyllanthus niruri, rice bran, and magnesium hydroxide. Several of the identified treatments may help prevent CaOx stone formation and may be useful for inclusion in kidney stone prevention guidelines.

Aim of the study: Progressive cardiac aging represents a major risk factor for heart diseases in the elderly population. Malic enzyme 1 (ME1) is an important regulator of redox homeostasis in multiple organs.

Results: Supplementation with L-malate (LM), the substrate of ME1, significantly prevents cardiomyocyte senescence both in vitro and in vivo. Mechanistically, the anti-aging effect of cardiac ME1 is dependent on its product nicotinamide adenine dinucleotide phosphate (NADPH), which promotes the enzymatic formation of nitric oxide (NO). Sufficient NO is essential for longevity, and inhibition of NO synthase (NOS) abolishes the cardioprotection provided by LM. Taken together, these findings show that targeting ME1 may offer new preventive or therapeutic approaches to age-associated cardiovascular diseases.

Results: Initially, a murine enteroendocrine STC-1 cell line is used to verify that coadministration of GABA and MA synergistically induces GLP-1 secretion. Next, 22 healthy adults are given water (50 mL) containing 400 mg GABA and 400 mg MA (Test), or only 400 mg citric acid (CA) (Placebo), 20 min before a meal tolerance test (MTT). Blood samples are taken at intervals for 180 min after the meal to measure GLP-1, insulin, and glucose responses. Compared with the Placebo preload, the Test preload significantly increases plasma GLP-1 (total/active) levels (incremental area under the curve by 1.2- and 1.6-fold, respectively). However, there are no significant differences in post-meal blood glucose or insulin. Taking GABA and MA together before meals enhances post-meal GLP-1 secretion. Future studies should explore optimal dosage regimens to determine the mixture's effects on insulin and glycemic response.

Aim of the study: Embryo loss during early pregnancy is a major constraint on mammalian reproductive efficiency. We previously revealed that dietary L-malic acid (L-MA) supplementation benefits maternal health in sows during late pregnancy.

Results: L-MA increased beneficial bacteria, including short-chain fatty acid (SCFA)-producing, anti-inflammatory, and antioxidant taxa, while reducing inflammation-associated bacteria. These specific taxa were significantly correlated with differences in metabolites, antioxidant and anti-inflammatory markers, and reproductive outcomes. Overall, our data showed that dietary L-MA supplementation during early pregnancy enhanced reproductive performance in sows. These benefits may be associated with changes in the maternal gut microbiota-metabolite axis and enhanced antioxidant and anti-inflammatory capacity. Therefore, L-MA supplementation may be a potential strategy to reduce embryo loss and improve reproductive performance in mammals.

Aim of the study: Potatoes with colored flesh are increasingly processed in the food industry. However, establishing appropriate production parameters is challenging because anthocyanins and other polyphenols present in potatoes undergo structural transformations during processing.

Results: Grits produced with malic and tartaric acids contained 20–67% more phenolic acids than the control and showed higher antioxidant activity. Lactic acid had an adverse effect, particularly in LR dehydrated potato grits. The effectiveness of organic acids in stabilizing anthocyanins varied depending on the potato cultivar. Therefore, processing conditions for colored potatoes should be optimized for each specific cultivar.

Aim of the study: Microalgae serve as a rich source of polyunsaturated fatty acids (PUFA), which are essential for human health and disease. Various plant growth regulators (PGRs) and exogenous chemicals such as malic acid (MA) play an important role in growth and stress-mediated metabolite production in microalgae.

Results: Docosahexaenoic acid (DHA) levels were higher in MA-treated cells, followed by NAA. MA was found to upregulate the expression of the fatty acid biosynthetic genes Δ5Des and Δ4Des, thereby improving EPA and DHA production. KIN increased GLA production by upregulating the Δ6Des gene, followed by MA. Compared with all other treatments, MA-treated cells showed a significant increase in total lipid content and PUFA production. PGRs and exogenous chemicals accelerate lipid biosynthesis by upregulating the expression of desaturase genes, thereby increasing levels of high-value PUFA.