The vicious cycle in the development of diabetes mellitus and sarcopenia in older persons

Proteomics Analysis Provides Insights into the Role of Lipid Metabolism in T2DM-Related Sarcopenia

Sarcopenia has been recognized as an emerging complication of type 2 diabetes mellitus (T2DM). Currently, the pathogenesis of T2DM-related sarcopenia remains unclear. The aim of this study was to investigate the molecular mechanisms and potential therapeutic targets for T2DM-related sarcopenia. In this study, a T2DM-related sarcopenia mouse model was established using db/db mice. Proteins extracted from the gastrocnemius muscles of db/db mice and littermate control db/m mice were analyzed by a 4D label-free quantitative proteomics approach. A total of 131 upregulated and 68 downregulated proteins were identified as differentially expressed proteins (DEPs). Bioinformatics analysis revealed that DEPs were significantly enriched in lipid metabolism. Protein-protein interaction network analysis revealed that six hub proteins, including ACOX1, CPT2, ECI2, ACADVL, ACADL, and ECH1, were involved in the fatty acid oxidation. The hub protein-transcription factor-miRNA network was also constructed using the NetworkAnalyst tool. Finally, the hub proteins were validated by Western blotting and immunohistochemistry and further confirmed to be significantly negatively correlated with muscle mass and grip strength. Our study suggested that lipid metabolism, especially excessive fatty acid oxidation, may be a crucial contributor to the progression of T2DM-related sarcopenia and a common cause of the inter-relationship between T2DM and sarcopenia. Targeting lipid metabolism may be a promising therapeutic strategy for T2DM-related sarcopenia.

Diabetes Mellitus Should Be Considered While Analysing Sarcopenia-Related Biomarkers

Sarcopenia is a chronic, progressive skeletal muscle disease characterised by low muscle strength and quantity or quality, leading to low physical performance. Patients with type 2 diabetes mellitus (T2DM) are more at risk of sarcopenia than euglycemic individuals. Because of several shared pathways between the two diseases, sarcopenia is also a risk factor for developing T2DM in older patients. Various biomarkers are under investigation as potentially valuable for sarcopenia diagnosis and treatment monitoring. Biomarkers related to sarcopenia can be divided into markers evaluating musculoskeletal status (biomarkers specific to muscle mass, markers of the neuromuscular junction, or myokines) and markers assuming causal factors (adipokines, hormones, and inflammatory markers). This paper reviews the current knowledge about how diabetes and T2DM complications affect potential sarcopenia biomarker concentrations. This review includes markers recently proposed by the expert group of the European Society for the Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) as those that may currently be useful in phase II and III clinical trials of sarcopenia: myostatin (MSTN); follistatin (FST); irisin; brain-derived neurotrophic factor (BDNF); procollagen type III N-terminal peptide (PIIINP; P3NP); sarcopenia index (serum creatinine to serum cystatin C ratio); adiponectin; leptin; insulin-like growth factor-1 (IGF-1); dehydroepiandrosterone sulphate (DHEAS); C-reactive protein (CRP); interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α). A better understanding of factors influencing these biomarkers' levels, including diabetes and diabetic complications, may lead to designing future studies and implementing results in clinical practice.

The Vicious Cycle of Type 2 Diabetes Mellitus and Skeletal Muscle Atrophy: Clinical, Biochemical, and Nutritional Bases

Today, type 2 diabetes mellitus (T2DM) and skeletal muscle atrophy (SMA) have become increasingly common occurrences. Whether the onset of T2DM increases the risk of SMA or vice versa has long been under investigation. Both conditions are associated with negative changes in skeletal muscle health, which can, in turn, lead to impaired physical function, a lowered quality of life, and an increased risk of mortality. Poor nutrition can exacerbate both T2DM and SMA. T2DM and SMA are linked by a vicious cycle of events that reinforce and worsen each other. Muscle insulin resistance appears to be the pathophysiological link between T2DM and SMA. To explore this association, our review (i) compiles evidence on the clinical association between T2DM and SMA, (ii) reviews mechanisms underlying biochemical changes in the muscles of people with or at risk of T2DM and SMA, and (iii) examines how nutritional therapy and increased physical activity as muscle-targeted treatments benefit this population. Based on the evidence, we conclude that effective treatment of patients with T2DM-SMA depends on the restoration and maintenance of muscle mass. We thus propose that regular intake of key functional nutrients, along with guidance for physical activity, can help maintain euglycemia and improve muscle status in all patients with T2DM and SMA.

Arginine and Lysine Supplementation Potentiates the Beneficial β-Hydroxy ß-Methyl Butyrate (HMB) Effects on Skeletal Muscle in a Rat Model of Diabetes

Skeletal muscle is the key tissue for maintaining protein and glucose homeostasis, having a profound impact on the development of diabetes. Diabetes causes deleterious changes in terms of loss of muscle mass, which will contribute to reduced glucose uptake and therefore progression of the disease. Nutritional approaches in diabetes have been directed to increase muscle glucose uptake, and improving protein turnover has been at least partially an oversight. In muscle, β-hydroxy β-methyl butyrate (HMB) promotes net protein synthesis, while arginine and lysine increase glucose uptake, albeit their effects on promoting protein synthesis are limited. This study evaluates if the combination of HMB, lysine, and arginine could prevent the loss of muscle mass and function, reducing the progression of diabetes. Therefore, the combination of these ingredients was tested in vitro and in vivo. In muscle cell cultures, the supplementation enhances glucose uptake and net protein synthesis due to an increase in the amount of GLUT4 transporter and stimulation of the insulin-dependent signaling pathway involving IRS-1 and Akt. In vivo, using a rat model of diabetes, the supplementation increases lean body mass and insulin sensitivity and decreases blood glucose and serum glycosylated hemoglobin. In treated animals, an increase in GLUT4, creatine kinase, and Akt phosphorylation was detected, demonstrating the synergic effects of the three ingredients. Our findings showed that nutritional formulations based on the combination of HMB, lysine, and arginine are effective, not only to control blood glucose levels but also to prevent skeletal muscle atrophy associated with the progression of diabetes.

Clinical impacts of frailty on 123,172 people with diabetes mellitus considering the age of onset and drugs of choice: a nationwide population-based 10-year trajectory analysis

AIMS

Frailty substantially increased the risk of adverse clinical outcomes, which was also critical in diabetes management. This study aimed to investigate the interrelationships between the age of onset, frailty, anti-diabetic medications and clinical outcomes in people with diabetes mellitus (DM).

METHODS

A total of 123,172 people aged 40 years and older who were newly diagnosed with DM were identified and categorised into four frailty subgroups (robust, mild, moderate and severe) based on the multimorbidity frailty index (mFI). Cox proportional hazards models were used to examine associations between frailty and clinical outcomes at different ages of DM onsets (40-64, 65-74, 75-84 and 85+ years). Outcomes of interest included generic outcomes (mortality and unplanned hospitalisation) and DM-related outcomes (cardiovascular disease-related mortality, major adverse cardiovascular events (MACEs), diabetes-related hospitalisation and hypoglycaemia).

RESULTS

The proportion of frailty increased with age at diagnosis amongst people with incident DM and the mFI scores increased significantly during the 10-year follow-up. Amongst people with diabetes, those with mild, moderate and severe frailty were associated with greater risks of all-cause mortality (mild: adjusted hazard ratio (aHR) 1.69 [95% confidence interval (CI) 1.60-1.80], P < 0.01; moderate: aHR 2.46 [2.29-2.65], P < 0.01; severe frailty: aHR 3.40 [3.16-3.65], P < 0.01) compared with the robust group. Similar results were found in unplanned hospitalisations, cardiovascular disease-related mortality, MACEs and hypoglycaemia.

CONCLUSIONS

Our study quantified the prevalence of frailty, captured its dynamic changes and examined its impacts on various clinical outcomes amongst people with diabetes at different ages at onset. Frailty assessment and management should be implemented into routine diabetes care.