Association between insulin resistance and lean mass loss and fat mass gain in older men without diabetes mellitus

The association between the triglyceride-glucose index and sarcopenia: data from the NHANES 2011-2018

BACKGROUND

The Triglyceride-glucose (TyG) index is a marker of insulin resistance, but its role in sarcopenia is controversial. The purpose of this study was to investigate the association of the TyG index with sarcopenia.

METHODS

4030 participants aged 20 years and above were selected from National Health and Nutrition Examination Survey for cross sectional study. Weighted logistic regression model was used to estimate the association between TyG index and sarcopenia. Threshold effect analysis and restricted cubic spline were employed to describe nonlinear link, with interaction tests and subgroup analyses performed.

RESULTS

It was found in the fully adjusted model that the TyG index was positively associated with sarcopenia (per 1-unit increase in the TyG index: OR = 1.31, 95%CI: 1.07, 1.60). This association was further highlighted in groups characterized by the absence of MetS or diabetes, as well as the absence of vigorous or moderate work activity. Furthermore, analysis of the curve fitting and threshold effects indicated a nonlinear relationship, which exhibited a turning point at 9.14.

CONCLUSION

The study results indicated that the TyG index was positively associated with sarcopenia. Enhancing the management of insulin resistance could help reduce the risk of developing sarcopenia.

Clinical outcomes of multidimensional association of type 2 diabetes mellitus, COVID-19 and sarcopenia: an algorithm and scoping systematic evaluation

BACKGROUND

The aim of this study was to provide a scoping and comprehensive review for the clinical outcomes from the cross-link of Type 2 diabetes mellitus (T2DM), COVID-19, and sarcopenia.

METHODS

By using PRISMA guidelines and searching through different databases that could provide findings of evidence on the association of T2DM, COVID-19, and sarcopenia.

RESULTS

Thirty-three studies reported a relationship between sarcopenia with T2DM, twenty-one studies reported the prognosis COVID-19 in patients with T2DM, ten studies reported the prognosis of COVID-19 in patients with sarcopenia, five studies discussed the outcomes of sarcopenia in patients with COVID-19, and one study reported sarcopenia outcomes in the presence of T2DM and COVID-19.

CONCLUSION

There is an obvious multidimensional relationship between T2DM, COVID-19 and sarcopenia which can cause prejudicial effects, poor prognosis, prolonged hospitalisation, lowered quality of life and a higher mortality rate during the current COVID-19 pandemic.

A Cross-Sectional Study on Metabolic Syndrome Parameters, the Nutritional Index, and Physical Status Associated with or Without the Possible Diagnosed Sarcopenia in Older Women Using A Propensity Score Matching Method

Objectives

To develop strategies against sarcopenia, physiological and biochemical data in older women were analyzed using propensity score matching.

Methods

Fifty-six women aged ≥75 years with the AWGS calf circumference <33 cm were included in the sarcopenia risk group. Low muscle strength (handgrip strength <18kg) or low physical performance (five-times-sit-to-stand test ≥12s) were used the possible-sarcopenia group. Propensity score matching adjusted for age and BMI was performed between the possible-sarcopenia group with low muscle strength (or physical performance) and the sarcopenia risk group without low muscle strength (or physical performance). The comparison included nutritional index, metabolic syndrome parameters, BMD, and skeletal muscle mass index score between both groups.

Results

The possible-sarcopenia group with low muscle strength exhibited significantly lower BMD (p=0.014) and skeletal muscle mass index score (p=0.002) compared to the sarcopenia risk group without low muscle strength. The possible-sarcopenia group with low physical performance exhibited significantly lower AST (p=0.034) compared to the sarcopenia risk group without low physical performance.

Conclusion

These results suggest that older women with possible sarcopenia and low muscle strength may have reduced BMD and skeletal muscle mass index.

Association of metabolic syndrome and sarcopenia with all-cause and cardiovascular mortality: a prospective cohort study based on the NHANES

Background

Metabolic syndrome (MetS) and sarcopenia (SP) have emerged as significant public health concerns in contemporary societies, characterized by shared pathophysiological mechanisms and interrelatedness, leading to profound health implications. In this prospective cohort study conducted within a US population, we aimed to examine the influence of MetS and SP on all-cause and cardiovascular mortality.

Methods

This study analyzed data from the National Health and Nutrition Examination Survey (NHANES) III for the years 1999-2006 and 2011-2018, and death outcomes were ascertained by linkage to National Death Index (NDI) records through December 31, 2019. Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) for all-cause and cardiovascular mortality. In addition, subgroup and sensitivity analyses were conducted to test the robustness of the results.

Results

Over a median follow-up period of 13.3 years (95% CI: 12.8-13.8), 1714 deaths were observed. The groups characterized by MetS-/SP+, MetS+/SP-, and MetS+/SP+ exhibited higher all-cause mortality rates in comparison to the MetS-/SP- group, with the MetS+/SP+ group (HR 1.76, 95% CI: 1.37-2.25) displaying the highest all-cause mortality. Increased cardiovascular mortality was observed in the MetS+/SP- (HR 1.84, 95% CI: 1.24-2.72), and MetS+/SP+ groups (HR 2.39, 95% CI: 1.32-4.35) compared to the MetS-/SP- group, whereas it was not statistically significant in the MetS-/SP+ group. However, among males and individuals aged < 60, the presence of both MetS and SP (MetS+/SP+ group) was found to be significantly associated with a higher risk of all-cause and cardiovascular mortality.

Conclusion

The coexistence of MetS and SP increased the risk of all-cause and cardiovascular mortality, particularly in males and in nonelderly populations. Individuals with either MetS or SP may require more careful management to prevent the development of other diseases and thereby reduce mortality.

Sonographic Measurements of Rectus Femoris Muscle Thickness Strongly Predict Neutropenia in Cancer Patients Receiving Chemotherapy

The objective of this study was to explore the possible association between low skeletal muscle mass (SMM)-assessed by computed tomography (CT) and ultrasound (US)-and hematologic toxicity in cancer patients. A prospective cohort study was conducted in cancer patients who received anthracycline-based chemotherapy between 2018 and 2020 and who had baseline abdominal CT including L3 level for measuring SMM. Regional muscle measurements were carried out using US. A total of 65 patients (14 males, 51 females) were included. ROC (receiver operating characteristic) analysis identified threshold values of 18.0 mm [AUC (area under the curve) = 0.765] for females and 20.0 mm (AUC = 0.813) for males, predicting severe neutropenia. Using these cut-offs, females with low rectus femoris (RF) thickness (<18.0 mm) had a significantly higher incidence of grade ≥3 neutropenia (50.0% vs. 10.8%, p = 0.005), and males with low RF values (<20.0 mm) had a higher incidence (80.0% vs. 22.2%, p = 0.063). A regression analysis, irrespective of age, gender, and body mass index, revealed that only low RF muscle thickness increased the risk of grade 3-4 neutropenia by 9.210 times (95% CI = 2.401-35.326, p = 0.001). Utilizing US to measure RF muscle thickness aids in identifying cancer patients at an elevated risk of developing neutropenia. Needless to say, US can serve as a convenient and easily accessible tool for assessing low SMM, providing repeat point-of-care evaluations in clinical practice.

A Randomized Controlled Trial Investigating the Impact of a Low-Calorie Dietary Approach to Stop Hypertension (DASH) on Anthropometric and Glycemic Measures in Patients Experiencing Weight Regain 2 Years Post Sleeve Surgery

PURPOSE

To evaluate the effect of a low-calorie dietary approach to stop hypertension (DASH) compared to a low-calorie diet on weight control, body composition and glycemic measures in post sleeve patients with weight regain.

MATERIALS AND METHODS

Participants were randomly allocated to either the low-calorie DASH diet group (intervention) or the low-calorie diet group (control) for a duration of 16 weeks. Both groups had a prescribed caloric intake of 1000-1200 calories. The DASH diet group made dietary adjustments in accordance with the DASH pattern.

RESULTS

At the end of the study, both interventions significantly reduced anthropometric and body composition parameters (P-value < 0.001), with a greater decrease observed in the low-calorie DASH diet group (P-value < 0.001). Insulin levels and homeostatic model assessment for insulin resistance (HOMA-IR) decreased significantly in both groups, but the magnitude of these changes was not statistically different between the two groups. After adjusting for confounders, a significant difference was observed in post-intervention values and changes in weight, body mass index, and fat mass and fat-free mass.

CONCLUSION

In summary, adhering to a calorie-restricted DASH diet for 16 weeks improved weight loss, body mass index, and fat mass reduction in post-bariatric patients who experienced weight regain 2 years after surgery, compared to a calorie-restricted control diet. However, there was no significant difference in the effect on blood glucose, insulin, and HOMA-IR between the two diets.

5'-Cytimidine Monophosphate Ameliorates H2O2-Induced Muscular Atrophy in C2C12 Myotubes by Activating IRS-1/Akt/S6K Pathway

Age-related muscle atrophy (sarcopenia), characterized by reduced skeletal muscle mass and muscle strength, is becoming increasingly prevalent worldwide, which is especially true for older people, and can seriously damage health and quality of life in older adults. This study aims to investigate the beneficial effects of 5'-cytimidine monophosphate (CMP) on H2O2-induced muscular atrophy in C2C12 myotubes. C2C12 myotubes were treated with H2O2 in the presence and absence of CMP and the changes in the anti-oxidation, mitochondrial functions, and expression of sarcopenia-related proteins were observed. Immunofluorescence analysis showed that CMP significantly increased the diameter of myotubes. We found that CMP could increase the activity of antioxidant enzymes and improve mitochondrial dysfunction, as well as reduce inflammatory cytokine levels associated with sarcopenia. RNA-seq analysis showed that CMP could relieve insulin resistance and promote protein digestion and absorption. Western blot analysis further confirmed that CMP could promote the activation of the IRS-1/Akt/S6K signaling pathway and decrease the expression of MuRF1 and Atrogin-1, which are important markers of muscle atrophy. The above results suggest that CMP protects myotubes from H2O2-induced atrophy and that its potential mechanism is associated with activating the IRS-1/Akt/S6K pathway to promote protein synthesis by improving mitochondrial dysfunction and insulin resistance. These results indicate that CMP can improve aging-related sarcopenia.

Association between the triglyceride glucose index and low skeletal muscle mass: a cross-sectional study

OBJECTIVES

Triglyceride glucose (TyG) represents a consistent surrogate biomarker and index of insulin resistance (IR), IR has also been linked to skeletal muscle mass loss (SMM-L). Here, we evaluated the association between SMM-L and the TyG index (TyGi).

DESIGN

An analytical cross-sectional study.

SETTING

Tertiary care hospitals.

PARTICIPANTS

36 275 participants who underwent health checks between 1 January 2013 and 31 December 2020.

PRIMARY AND SECONDARY OUTCOME MEASURES

A bioelectrical impedance analysis was used to assess the body composition, SMM-L was defined as low ASMI (total limb lean mass/height2) and TyGi was calculated as ln(triglycerides (mg/dL)×fasting blood glucose (mg/dL)/2).

RESULTS

A total of 36 275 subjects were included in the study, of which 58.46% were male, with a mean age of 43.74±12.33 years. The prevalence of low skeletal muscle mass (SMM) was 17.7% and the mean TyGi was 8.56±0.64. TyGi was found to be significantly correlated with low SMM in all subjects (OR 1.87, 95% CI 1.75 to 2.00, p<0.001), with higher correlations seen in younger subjects (OR 1.97, 95% CI 1.77 to 2.20, p<0.001), and remaining significant in middle age (OR 1.95, 95% CI 1.77 to 2.14, p<0.001), old age (OR 1.73, 95% CI 1.38 to 1.16, p<0.001), men (OR 1.60, 95% CI 1.46 to 1.76, p<0.001) and women (OR 2.59, 95% CI 2.39 to 2.87, p<0.001).

CONCLUSIONS

These data demonstrated a significant independent interaction between TyGi and low SMM in all subjects regardless of sex and age subgroups in the general population.

Pathogenesis and comprehensive treatment strategies of sarcopenia in elderly patients with type 2 diabetes mellitus

Sarcopenia and diabetes are two age-related diseases that are common in the elderly population, and have a serious effect on their general health and quality of life. Sarcopenia refers to the progressive loss of muscle mass, strength and function, whereas diabetes is a chronic disease characterized by elevated blood sugar levels. The comorbidity of sarcopenia and diabetes is particularly concerning, as people with diabetes have a higher risk of developing sarcopenia due to the combination of insulin resistance, chronic inflammation and reduced physical activity. In contrast, sarcopenia destroyed blood sugar control and exacerbated the development of people with diabetes, leading to the occurrence of a variety of complications. Fortunately, there are a number of effective treatment strategies for sarcopenia in people with diabetes. Physical exercise and a balanced diet with enough protein and nutrients have been proved to enhance the muscular quality and strength of this population. Additionally, pharmacological therapies and lifestyle changes can optimize blood sugar control, which can prevent further muscle loss and improve overall health outcomes. This review aims to summarize the pathogenesis and comprehensive treatment strategies of sarcopenia in elderly patients with type 2 diabetes, which help healthcare professionals recognize their intimate connection and provide a new vision for the treatment of diabetes and its complications in this population. Through early identification and comprehensive treatment, it is possible to improve the muscle function and general quality of life of elderly with diabetes and sarcopenia.

The Hidden Battle Within: Shedding Light on the Co-existence of Sarcopenia and Sarcopenic Obesity among Participants with Type 2 Diabetes in a Tertiary Care Hospital, Gujarat

Introduction

Type 2 diabetes (T2DM) is characterised by chronic hyperglycaemia due to abnormal insulin secretion and/or utilisation. Currently, sarcopenia has emerged as a new complication of T2DM, which increases the risk of physical disability, and even death. The study aims to estimate the prevalence of sarcopenia and sarcopenic obesity (SO) as well as their association with various other factors related to T2DM.

Methods

The study was an observational hospital-based cross-sectional study conducted among diabetic patients who came to the non-communicable diseases (NCD) clinic of a tertiary care hospital in Gujarat, India, from April 2023 to June 2023. Adult patients with T2DM attending follow-ups were included, with a diagnosis of T2DM for at least 1 year from the date of their electronic medical records, regardless of their mode of therapeutic treatment. They were on regular medical reviews with two or more visits to the study site in the past 1 year. Then a self-structured standard questionnaire was used to collect the data, containing socio-demographic characteristics, clinical profiles, anthropometric assessment (comprising weight, height and body mass index [BMI]), bio-impedance indices like body fat%, skeletal muscle% and handgrip by hand dynamometer.

Results

In the study, a total of 404 participants participated. Their mean age was 55 ± 13.5 years and their mean body fat (BF) % was 30 ± 7.4%. BF%-defined obesity was found in 260 (64.4%) participants. A total of 362 (89.6%) had possible sarcopenia, 183 (45.3%) had sarcopenia and 124 (30.7%) had SO. Age (OR: 2.6, CI: 1.7-3.9), duration of diabetes for more than 7 years (OR: 7.5, CI: 3.65-15.4) and BF%-defined obesity (OR: 2.2, CI: 3.6-15) were statistically associated with Sarcopenia, in similar pattern age (OR: 2.4, CI: 1.5-3.7), and duration of diabetes more than 7 years (OR: 18.9, CI: 5.7-62) were associated with SO (P < 0.05).

Conclusion

Older age, longer diabetes duration and BF%-defined obesity are associated with an increased likelihood of developing sarcopenia and sarcopenic obesity. Healthcare providers should prioritise regular screening for sarcopenia and SO in elderly individuals with diabetes to facilitate early detection and intervention.

Stimulator of interferon genes promotes diabetic sarcopenia by targeting peroxisome proliferator activated receptors γ degradation and inhibiting fatty acid oxidation

BACKGROUND

Declined skeletal muscle mass and function are inevitable consequences of long-term diabetes and bring about many adverse events. Muscle fibre atrophy and interstitial fibrosis are major pathological manifestations of diabetic sarcopenia. Stimulator of interferon genes (STING) participates in various metabolic diseases. We aimed to explore whether and how STING regulates the above pathological manifestations of diabetic sarcopenia.

METHODS

Wild-type and STINGgt/gt C57BL/6J mice and C2C12 myotubes were used to study the role of STING in the regulation of diabetic sarcopenia and the underlying mechanisms.

RESULTS

STING was abnormally activated in diabetic muscles and in PA-treated myotubes (P < 0.01 for all parameters). The diabetic mice demonstrated decreased forelimb grip strength, lean mass, muscle weight and hanging impulse, which were improved by STING deficiency due to alleviated muscle fibre atrophy and interstitial fibrosis (P < 0.05 for all parameters). STING deficiency alleviated muscle fibre atrophy through the following mechanisms. Firstly, STING deficiency or inhibition increased the contents of pDRP1Ser616 , PINK1, Parkin and LC3-II, decreased p62 content, and increased the amount of mito-Keima fluorescent dots at 578 nm in diabetic state (P < 0.05 for all parameters), suggesting improved mitofission and mitophagy. Secondly, STING deficiency or inhibition increased the expression of pAKTSer473 and GLUT4 post-insulin change in diabetic state (P < 0.05 for all), indicating alleviated insulin resistance (IR). Mechanically, STING deficiency or inhibition increased peroxisome proliferator activated receptors γ (PPARγ) protein content by reducing the degradation of ubiquitinated PPARγ through the proteasome pathway and thus increased the expression of fatty acid oxidation (FAO)-related proteins in diabetic state (P < 0.05 for all parameters). Decreased expression of FAO-related proteins caused by PPARγ inhibition abolished the improvements in mitofission, mitophagy and IR achieved by STING inhibition in PA-treated myotubes and thus promoted muscle fibre atrophy (P < 0.05 for all parameters). STING deficiency alleviated interstitial fibrosis by decreasing TGFβ1 expression in diabetic state and TGFβ1 promoted the fibrogenic differentiation of fibro-adipogenic progenitors (P < 0.05 for all parameters). PPARγ inhibition abolished the effect of STING inhibition on reducing TGFβ1 content in PA-treated myotubes (P < 0.01).

CONCLUSIONS

STING deficiency exerted protective effects in diabetic sarcopenia by inhibiting the degradation of ubiquitinated PPARγ through the proteasome pathway and enhancing PPARγ-mediated FAO, which alleviated muscle fibre atrophy by promoting mitophagy and ameliorating IR, and alleviated interstitial fibrosis by reducing TGFβ1 production and suppressing the fibrogenic differentiation of fibro-adipogenic progenitors.

Association between Sarcopenia and Poor Glycemic Control in Older Adults with Type 2 Diabetes Mellitus

BACKGROUND

Aging is associated with a decrease in muscle mass. Insulin resistance and hyperglycemia accelerate muscle loss, leading to a deterioration in strength, muscle mass, and physical capacity in older adults. This study was conducted to determine the association between sarcopenia and poor glycemic control in older adults with type 2 diabetes mellitus (T2D).

METHODS

A cross-sectional study was carried out in older adults with T2D in geriatric outpatient clinics. Sarcopenia was diagnosed as per the European Working Group on Sarcopenia in Older People 2 (EWGSOP2) criteria. According to glycosylated hemoglobin (HbA1c) levels, participants were classified into glycemic control (HbA1c ≤ 7.5%) and poor glycemic control (HbA1c ≥ 7.5%) groups.

RESULTS

Older adults with sarcopenia were found to have poor glycemic control compared to adults without sarcopenia (62.3% vs. 47.9%, p = 0.007). Logistic regression analysis showed an association between poor glycemic control and the presence of sarcopenia (odds ratio (OR): 1.79, 95% confidence interval (CI): 1.17-2.75) and low muscle mass (OR: 1.73, 95% CI: 1.07-2.73).

CONCLUSIONS

Poor glycemic control is associated with the presence of sarcopenia and low muscle mass, which highlights the need to implement better treatment strategies in order to reduce the loss of muscle mass.

Additive impact of diabetes and sarcopenia on all-cause and cardiovascular mortality: A longitudinal nationwide population-based study

OBJECTIVE

Diabetes mellitus (DM) and sarcopenia (SP) are growing public health concerns in an aging society, which share common pathophysiological mechanisms and are associated with serious health consequences. We investigated the impact of DM and SP on all-cause and cardiovascular mortalities in a longitudinal nationwide population-based study.

METHODS

The study analyzed data from the Korea National Health and Nutrition Examination Survey conducted between 2008 and 2011, including information on appendicular skeletal muscle mass data. Mortality data up to December 2020 were retrieved from the National Death Registry.

RESULTS

Among the 17,920 participants, 14,737 (82.2 %) had neither DM nor SP (DM-/SP-), 1349 (7.5 %) had only DM (DM+/SP-), 1425 (8.0 %) had only SP (DM-/SP+), and 409 (2.3 %) had both DM and SP (DM+/SP+). Compared to the DM-/SP- group, the DM-/SP+ and DM+/SP+ groups demonstrated increased all-cause mortality with adjusted hazard ratios (HRs) of 1.47 (95 % confidence interval [CI]: 1.14-1.89) and 1.85 (95 % CI: 1.28-2.69), respectively, while the DM+/SP- group did not (HR 1.29, 95 % CI: 0.97-1.74). The DM+/SP+ group demonstrated the highest risk of overall mortality (p-for-trend <0.001). Compared to the DM-/SP- group, only the DM+/SP+ group demonstrated increased cardiovascular mortality with HRs of 2.10 (95 % CI: 1.11-4.00) while the DM+/SP- (HR 1.35, 95 % CI: 0.79-2.30) and DM-/SP+ (HR 1.42, 95 % CI: 0.84-2.43) groups did not.

CONCLUSIONS

The coexistence of DM and SP additively increased the risk of all-cause and cardiovascular mortality. Individuals with either disease may require more careful management to prevent the development of the other disease to reduce mortality.

Repurposing Drugs for Diabetes Mellitus as Potential Pharmacological Treatments for Sarcopenia - A Narrative Review

Sarcopenia, the age-related loss of muscle strength and mass or quality, is a common condition with major adverse consequences. Although the pathophysiology is incompletely understood, there are common mechanisms between sarcopenia and the phenomenon of accelerated ageing seen in diabetes mellitus. Drugs currently used to treat type 2 diabetes mellitus may have mechanisms of action that are relevant to the prevention and treatment of sarcopenia, for those with type 2 diabetes and those without diabetes. This review summarises shared pathophysiology between sarcopenia and diabetes mellitus, including the effects of advanced glycation end products, mitochondrial dysfunction, chronic inflammation and changes to the insulin signalling pathway. Cellular and animal models have generated intriguing, albeit mixed, evidence that supports possible beneficial effects on skeletal muscle function for some classes of drugs used to treat diabetes, including metformin and SGLT2 inhibitors. Most human observational and intervention evidence for the effects of these drugs has been derived from populations with type 2 diabetes mellitus, and there is a need for intervention studies for older people with, and at risk of, sarcopenia to further investigate the balance of benefit and risk in these target populations. Not all diabetes treatments will be safe to use in those without diabetes because of variable side effects across classes. However, some agents [including glucagon-like peptide (GLP)-1 receptor agonists and SGLT2 inhibitors] have already demonstrated benefits in populations without diabetes, and it is these agents, along with metformin, that hold out the most promise for further investigation in sarcopenia.

Evidence That Increasing Serum 25(OH)D Concentrations to 30 ng/mL in the Kingdom of Saudi Arabia and the United Arab Emirates Could Greatly Improve Health Outcomes

Accumulating evidence supports the potential protective effects of vitamin D against chronic diseases such as Alzheimer’s disease, autoimmune diseases, cancers, cardiovascular disease (ischaemic heart disease and stroke), type 2 diabetes, hypertension, chronic kidney disease, stroke, and infectious diseases such as acute respiratory tract diseases, COVID-19, influenza, and pneumonia, as well as adverse pregnancy outcomes. The respective evidence is based on ecological and observational studies, randomized controlled trials, mechanistic studies, and Mendelian randomization studies. However, randomized controlled trials on vitamin D supplementation have largely failed to show benefits, probably due to poor design and analysis. In this work, we aim to use the best available evidence on the potential beneficial effects of vitamin D to estimate the expected reduction in incidence and mortality rates of vitamin D-related diseases in the Kingdom of Saudi Arabia and the United Arab Emirates if minimum serum 25(OH)D concentrations were to be raised to 30 ng/mL. Estimated reductions by 25% for myocardial infarction incidence, 35% for stroke incidence, 20 to 35% for cardiovascular disease mortality, and 35% for cancer mortality rates depicted a promising potential for raising serum 25(OH)D. Methods to increase serum 25(OH)D concentrations at the population level could include food fortification with vitamin D3, vitamin D supplementation, improved dietary vitamin D intake, and sensible sun exposure.

Association of skeletal muscle mass and its change with diabetes occurrence: a population-based cohort study

BACKGROUND

Low muscle mass likely results in reduced capacity for glucose disposal, leading to a significant but under-appreciated contribution to increasing the risk of diabetes. But few prospective studies have investigated the association between the loss of muscle mass and the occurrence of diabetes. We aimed to investigate whether short-term changes in muscle mass affect the incidence of diabetes in a Chinese population.

METHODS

This study included 1275 individuals without evident diabetes at baseline. In the baseline and re-examination, individuals completed the risk factors survey and underwent body composition measurement. Muscle mass index was defined as the percentage skeletal muscle mass, which was measured by an automatic bioelectric analyzer.

RESULTS

After a median follow-up of 2.1 years, 142 individuals developed diabetes (11.1%). There was an inverse association between basal skeletal muscle mass index and the risk of diabetes in participants with impaired glucose regulation but not in those with normal glucose tolerance. Multivariate-adjusted hazard ratios for the risk of developing diabetes were 0.85 (95% CI: 0.74-0.98) and 1.15 (95% CI: 0.98-1.34), respectively. Furthermore, Cox regression analysis revealed that a two-year change in skeletal muscle mass was also inversely associated with the incidence of diabetes in both participants with normal glucose tolerance and with impaired glucose regulation (HR: 0.76, 95% CI: 0.65-0.89; HR: 0.81, 95% CI: 0.71-0.91).

CONCLUSIONS

These findings emphasized the importance of early detection and control of muscle mass loss for the prevention of diabetes.

Preserved Lower Limb Muscle Mass Prevents Insulin Resistance Development in Nondiabetic Older Adults

OBJECTIVE

To investigate roles of sarcopenia indexes in prediction of development of insulin resistance in nondiabetic older adults.

DESIGN

A 2-year follow-up cohort.

SETTING AND PARTICIPANTS

The Tanno-Sobetsu study, a prospective observational cohort, included 194 community-dwelling nondiabetic older adults during 2017-2019.

METHODS

Lower limb, upper limb, appendicular, and trunk muscle masses by a bioelectrical impedance analysis, grip strength, knee extension torque, and walking speed were measured in study participants aged ≥65 years (79 men and 115 women) at baseline. Muscle mass and strength were divided by the weight, and then multiplied by 100 to calculate the weight ratio (%). Insulin resistance was assessed by homeostasis model (HOMA-IR) at baseline, and the study participants whose HOMA-IR was less than 1.73 at baseline were followed for a maximum of 2 years. The study endpoint was development of insulin resistance defined as HOMA-IR ≥1.73. The adjusted hazard ratio (HR) of each sarcopenia component for development of insulin resistance was calculated.

RESULTS

Lower limb muscle mass (HR 0.88, 95% CI 0.79-0.98) and appendicular muscle mass (HR 0.89, 95% CI 0.81-0.99), but not other sarcopenia components, were associated with the development of insulin resistance, independently of sex and age, HOMA-IR, and waist circumference at baseline.

CONCLUSIONS AND IMPLICATIONS

The loss of lower limb muscle mass is a significant risk factor for development of insulin resistance independently of obesity in nondiabetic older adults. The lower limb muscle mass may be a novel target of interventions for the prevention of diabetes in older adults.

Association between dietary inflammatory index score and muscle mass and strength in older adults: a study from National Health and Nutrition Examination Survey (NHANES) 1999-2002

PURPOSE

Chronic low-grade systemic inflammation affects muscle protein metabolism. The dietary inflammatory index (DII®) is a tool designed to assess the inflammatory potential of the diet. The available data on the association between DII and sarcopenia are limited. We aimed to investigate the association of the DII with components of sarcopenia in individuals over 50 years of age.

METHODS

This cross-sectional study used the National Health and Nutrition Examination Survey (NHANES) 1999-2002 dataset. Body composition was measured, and isokinetic strength of the knee extensors (peak force) was evaluated. Low muscle mass and strength were defined using sex-specific thresholds. Energy-adjusted DII (E-DII™) scores were calculated using 24-h dietary recall data. Regression models were fit to evaluate the association between E-DII scores and low muscle mass and low muscle strength, alone and combined.

RESULTS

Mean age of study participants was 62.1 ± 9.5 years, and 138 participants (7.4%) belonged to the combination group of low muscle mass and low muscle strength. In multivariable-adjusted regression models, higher E-DII score was associated with lower appendicular skeletal muscle index (ASMI) (β =  - 0.03, P  < 0.001, P trend <0.001), and lower peak force (β =  -2.15, P  = 0.04, P trend = 0.01) and higher likelihood for these components combined (OR = 1.12, 95% CI 1.01-1.25, P = 0.03).

CONCLUSION

Higher E-DII score is associated with lower muscle mass and muscle strength, and increased likelihood for the combination of low muscle mass and low muscle strength in older adults. This has important implications for healthy aging.

Association of the triglyceride-glucose index with weight-adjusted appendicular lean mass in Chinese adolescents aged 12-18 years old

There is no study exploring the association between triglyceride-glucose (TyG) index and skeletal muscle mass in Chinese adolescents. Therefore, the objective of this study is to explore the association between TyG index and appendicular lean mass (ALM) in Chinese adolescents. In this study, 1336 adolescents (805 boys, 60.25%) aged 12-18 years in China were randomly selected through a stratified cluster sampling. According to the tertiles of TyG index, we separated all participants into three groups, and LM was measured by Bioelectrical Impedance Analysis. The TyG index was negatively related to ALM/weight in Chinese adolescents whether stratified by gender (boys: β = - 0.293; girls: β = - 0.195; all P < 0.001). After adjusting for age and BMI, a significant correlation between the TyG index and ALM/weight was observed only in boys (β = - 0.169, P = 0.001). The highest TyG index tertile was significantly associated with low ALM/weight after adjusting for all covariates in the full sample (OR = 3.04, 95% CI 1.12-8.26, P = 0.029) and boys (OR = 4.68, 95% CI 1.22-17.95, P = 0.025) only in overweight/obese group. Our findings suggested elevated levels of TyG index may be a risk factor of low ALM/weight in Chinese adolescents, especially in boys.

Physiological Systems in Promoting Frailty

Frailty is a complex syndrome affecting a growing sector of the global population as medical developments have advanced human mortality rates across the world. Our current understanding of frailty is derived from studies conducted in the laboratory as well as the clinic, which have generated largely phenotypic information. Far fewer studies have uncovered biological underpinnings driving the onset and progression of frailty, but the stage is set to advance the field with preclinical and clinical assessment tools, multiomics approaches together with physiological and biochemical methodologies. In this article, we provide comprehensive coverage of topics regarding frailty assessment, preclinical models, interventions, and challenges as well as clinical frameworks and prevalence. We also identify central biological mechanisms that may be at play including mitochondrial dysfunction, epigenetic alterations, and oxidative stress that in turn, affect metabolism, stress responses, and endocrine and neuromuscular systems. We review the role of metabolic syndrome, insulin resistance and visceral obesity, focusing on glucose homeostasis, adenosine monophosphate-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), and nicotinamide adenine dinucleotide (NAD+ ) as critical players influencing the age-related loss of health. We further focus on how immunometabolic dysfunction associates with oxidative stress in promoting sarcopenia, a key contributor to slowness, weakness, and fatigue. We explore the biological mechanisms involved in stem cell exhaustion that affect regeneration and may contribute to the frailty-associated decline in resilience and adaptation to stress. Together, an overview of the interplay of aging biology with genetic, lifestyle, and environmental factors that contribute to frailty, as well as potential therapeutic targets to lower risk and slow the progression of ongoing disease is covered. © 2022 American Physiological Society. Compr Physiol 12:1-46, 2022.

Evaluation of knowledge, barriers, and attitudes in the management of type 2 diabetes in elderly patients: A Delphi study on primary and hospital care

OBJECTIVES

This work aims to explore attitudes regarding the management of elderly or frail patients with type 2 diabetes mellitus in the routine clinical practice of a multidisciplinary group of physicians in Spain.

METHODS

A mixed survey was used that included both Delphi and opinion, attitude, and behaviour (OAB) questions. Perceptions in primary care (n = 211) and hospital care (n = 80) were compared.

RESULTS

Consensus was obtained on all statements. Eighty-seven percent of participants considered that severe psychiatric disorders conditioned antidiabetic treatment and 72% that a psychocognitive assessment is as relevant as the assessment of other comorbidities. Hospital care physicians more frequently considered that comorbidity affects self-care (95.0% vs. 82.9%), that a lack of de-intensification is a form of therapeutic inertia (88.8% vs. 76.3%), that classifying older adults as frail is fundamental to choosing targets (96.3% vs. 87.7%), that de-intensification of antidiabetic treatment and control of cardiovascular risk factors should be considered in those over 80 years of age (90.0% vs. 78.7%), and that type 2 diabetes mellitus predisposes patients to sarcopenia (86.3% vs. 71.6%). The usefulness of clinical guidelines was more highly valued among primary care participants (79.1% vs. 72.5%).

CONCLUSIONS

There is room for improvement on several aspects of managing elderly or frail patients with type 2 diabetes mellitus, including inertia in treatment de-intensification, conducting a psychocognitive assessment, or the identification of frailty and sarcopenia.

Relationship between creatinine to body weight ratios and diabetes mellitus: A Chinese cohort study

BACKGROUND

Research on the relationship between creatinine to body weight ratios (Cre/BW ratios) and the prevalence of diabetes is still lacking. The intention of this research was to explore the potential relationship between Cre/BW ratio and diabetes prevalence in Chinese adults.

METHODS

This retrospective study was conducted on 199 526 patients in the Chinese Rich Healthcare Group from 2010 to 2016. The participants were divided into four groups on the basis of the quartiles of the Cre/BW ratios. Multivariate multiple imputation and dummy variables were used to handle missing values. Multivariate regression analysis was applied to detect the relationship between Cre/BW and diabetes. A smoothing plot was also used to identify whether there were nonlinear relationships.

RESULTS

After handling missing values and adjusting for potential confounders, the multivariate Cox regression analysis results showed that Cre/BW was inversely correlated with diabetes risk (hazard ratio [HR]: 0.268; 95% confidence interval [CI]: 0.229-0.314, p < 0.00001). For men, the HR of incident diabetes was 0.255 (95% CI: 0.212-0.307) and for women it was 0.297 (95% CI: 0.218-0.406). Moreover, sensitivity analysis confirmed the stability of the results. Furthermore, the smoothing plot revealed that there was a saturation effect between Cre/BW and the incidence of diabetes.

CONCLUSIONS

This study demonstrated that increased Cre/BW is negatively correlated with diabetes in Chinese adults. It also found that Cre/BW has a nonlinear relationship with the incidence of diabetes.

Skeletal muscle as a treatment target for older adults with diabetes mellitus: The importance of a multimodal intervention based on functional category

Although the lifespan of people with diabetes has increased in many countries, the age-related increase in comorbidities (sarcopenia, frailty and disabilities) and diabetic complications has become a major issue. Diabetes accelerates the aging of skeletal muscles and blood vessels through mechanisms, such as increased oxidative stress, chronic inflammation, insulin resistance, mitochondrial dysfunction, genetic polymorphism (fat mass and obesity-associated genes) and accumulation of advanced glycation end-products. Diabetes is associated with early onset, and progression of muscle weakness and sarcopenia, thus resulting in diminished daily life function. The type and duration of diabetes, insulin section/resistance, hyperglycemia, diabetic neuropathy, malnutrition and low physical activity might affect muscular loss and weakness. To prevent the decline in daily activities in older adults with diabetes, resistance training or multicomponent exercise should be recommended. To maintain muscle function, optimal energy and sufficient protein intake are necessary. Although no specific drug enhances muscle mass and function, antidiabetic drugs that increase insulin sensitivity or secretion could be candidates for improvement of sarcopenia. The goals of glycemic control for older patients are determined based on three functional categories through an assessment of cognitive function and activities of daily living, and the presence or absence of medications that pose a hypoglycemic risk. As these functional categories are associated with muscle weakness, frailty and mortality risk, providing multimodal interventions (exercise, nutrition, social network or support and optimal medical treatment) is important, starting at the category II stage for maintenance or improvement in daily life functions. Geriatr Gerontol Int 2022; ••: ••-••.

Interaction effect of systemic inflammation and modifiable rheumatoid cachexia risk factors on resting energy expenditure in patients with rheumatoid arthritis

Background

In rheumatoid cachexia (RC), high resting energy expenditure (REE) is associated with loss of muscle mass driven by proinflammatory cytokines. The objectives of this study were to investigate parameters associated with RC, and the interaction between systemic inflammation and modifiable risk factors for RC on REE.

Methods

Thirty-five rheumatoid arthritis (RA) and nineteen non-RA controls comparable in age, sex, race and BMI underwent measures of REE by indirect calorimetry. Clinical, dietary, body composition and physical function data were collected. Homeostasis model assessment for insulin resistance (HOMA-IR) and serum interleukin-6 (IL-6) were used as parameters of IR and systemic inflammation, respectively. Regression models tested association between REE and dependent variables, including pre-specified interaction tests involving HOMA-IR and IL-6 and dietary intake of protein per weight (PPW) and IL-6.

Results

RA subjects were mostly women (94%) and had a median age of 54 years (50.5, 70) and BMI of 30.5 kg/m2 (26.1, 36.9). We observed a significant interaction effect between PPW and serum IL-6 on REE among RA subjects in the multiple regression model among RA. The upper tertile of PPW demonstrated a significant negative correlation between REE and IL-6 (β=-19.97, 95% CI [-35.41, -4.54], p=0.01). The lower tertile of PPW demonstrated a significant positive correlation between REE and IL-6 (β=42.24, 95% CI [4.25, 80.23], p=0.03).

Conclusions

While IR can lead to muscle catabolism, IR was not significantly associated with REE in RA individuals. Higher dietary protein intake could attenuate the effect of systemic inflammation on REE in RA patients.

Sex-Specific Associations Between Low Muscle Mass and Glucose Fluctuations in Patients With Type 2 Diabetes Mellitus

OBJECTIVE

Studies have shown that sex differences in lean mass, concentrations of sex hormones, and lifestyles influence cle health and glucose metabolism. We evaluated the sex-specific association between low muscle mass and glucose fluctuations in hospitalized patients with type 2 diabetes mellitus (T2DM) receiving continuous subcutaneous insulin infusion (CSII) therapy.

METHODS

A total of 1084 participants were included. Body composition was determined by dual-energy X-ray absorptiometry. Intraday blood glucose fluctuation was estimated by the Largest amplitude of glycemic excursions (LAGE) and standard deviation of blood glucose (SDBG).

RESULTS

The prevalence of low muscle mass was higher in males than in females (p<0.001). There was a significant sex-specific interaction between the status of low muscle mass and glucose fluctuations (LAGE and SDBG) (p for interaction=0.025 and 0.036 for SDBG and LAGE, respectively). Among males, low muscle mass was significantly associated with a higher LAGE and SDBG (difference in LAGE: 2.26 [95% CI: 1.01 to 3.51], p < 0.001; difference in SDBG: 0.45 [95% CI: 0.25 to 0.65], p < 0.001) after adjustment for HbA1c, diabetes duration, hyperlipidemia, diabetic peripheral neuropathy, diabetic nephropathy, and cardiovascular disease. These associations remained significant after further adjustment for age and C-peptide. Among females, low muscle mass was not associated with LAGE or SDBG after adjustment for all covariates.

CONCLUSION

The prevalence of low muscle mass was higher in males than in females. Low muscle mass was significantly associated with higher LAGE and SDBG among males, but not females.

High Serum AST/ALT Ratio and Low Serum INS*PA Product Are Risk Factors and Can Diagnose Sarcopenia in Middle-Aged and Older Adults

BACKGROUND

Sarcopenia is an age-related clinical condition and associated with an increased risk of adverse outcomes. However, to date, there is no global standard for the diagnosis of sarcopenia, and fewer serum biomarkers have been suggested for the diagnosis of sarcopenia. It is, thus, important that sarcopenia-related serological diagnostic markers be explored. The present study was based on the Asian Working Group on Sarcopenia 2019 (AWGS 2019) criteria to assess whether aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio and fasting insulin*prealbumin (INS*PA) product are diagnostic markers associated with sarcopenia in various ethnic groups in western China.

METHODS

This cross-sectional study included 4,099 adults (1,471 men and 2,628 women) from the West China Health and Aging Trend (WCHAT) study. The value of serum biomarkers was based on laboratory data. The accompanying metabolic disorders and the associated parameters were evaluated. Logistic regression analysis was used to explore the association between markers and sarcopenia. Receiver operating characteristic curve (ROC) analysis was used to evaluate the diagnostic efficacy of the test in differentiating sarcopenia.

RESULTS

Binary regression analysis showed that high serum AST/ALT (OR = 2.247) and adrenal cortisol (PTC, OR = 1.511), low serum INS*PA (OR = 2.970), free triiodothyronine (FT3, OR = 1.313), 25-OH-VitD (VitD, in male participants, OR = 1.817), and diastolic blood pressure (DBP, in female subjects, OR = 1.250) were independent risk factors for sarcopenia (P < 0.05). AST/ALT and INS*PA were not affected by metabolic factors and had better diagnostic efficacy for sarcopenia. The AUC of the INS*PA was the highest (0.705, 0.706, and 0.701, respectively, P < 0.05), followed by that of the AST/ALT (0.680, 0.675, and 0.695, respectively, P < 0.05). The AUC of the AST/ALT/(INS*PA)*10,000 used to diagnose sarcopenia was 0.727.

CONCLUSION

Among middle-aged and older adults of multiple ethnicities in western China, we found that higher AST/ALT and lower INS*PA levels are associated with an increased prevalence of sarcopenia. Since these serum biomarkers are inexpensive and can be obtained easily from biochemical routine, regular follow-up of AST/ALT and INS*PA may be an effective strategy in sarcopenia screening and management.

Ground reaction force and electromyograms of lower limb muscles during fast walking

Background

Physically active status is an important contributor to individual health. Walking is regarded as commonly accepted exercise for exercise promotion. Particularly, interval fast walking (FW), consisting of alternating between fast and slow walking speeds, has gained popularity from practical viewpoints. Although previous studies have determined the short- and long-term effects of FW programs on endurance capacity and cardiovascular variables, factors affecting these outcomes have not been clarified. In addition to physiological variables, understanding of mechanical variables and muscle activity during FW would be a help to understand characteristics of FW. In the present study, we compared the ground reaction force (GRF) and lower limb muscle activity between fast walking (FW) and running at equivalent speeds.

Method

Eight healthy men performed slow walking (45% of the maximum walking speed; SW, 3.9 ± 0.2 km/h), FW (85% of the maximum walking speed, 7.4 ± 0.4 km/h), and running at equivalent speeds (Run) for 4 min each. GRF and average muscle activity (aEMG) were evaluated during the contact, braking, and propulsive phases. Muscle activities were determined for seven lower limb muscles: gluteus maximus (GM), biceps femoris (BF), rectus femoris (RF), vastus lateralis (VL), gastrocnemius medialis (MG), soleus (SOL), and tibialis anterior (TA).

Results

The anteroposterior GRF was greater in FW than in Run during the propulsive phase (p < 0.001), whereas the impact load (peak and average vertical GRF) was lower in FW than in Run (p < 0.001). In the braking phase, lower leg muscle aEMGs were higher during Run than during SW and FW (p < 0.001). However, in the propulsive phase, soleus muscle activity was greater during FW than during Run (p < 0.001). aEMG of tibialis anterior was higher during FW than during SW and Run in the contact phase (p < 0.001). No significant difference between FW and Run was observed for HR and RPE.

Conclusion

These results suggest that the average muscle activities of lower limbs (e.g., gluteus maximus, rectus femoris, and soleus) during the contact phase were comparable between FW and running, however, the activity patterns of lower limb muscles differed between FW and running, even at equivalent speeds. During running, muscles were mainly activated in the braking phase related to impact. In contrast, during FW, soleus muscle activity during the propulsive phase was increased. Although cardiopulmonary response was not different between FW and running, exercise using FW might be useful for health promotion among individuals who cannot exercise at high-intensity.

Truncal Fat and Frailty Are Important Predictors of Cognitive Performance among Aging Adults with Obesity

OBJECTIVES

To explore associations among cognition, frailty, and obesity in older adults.

DESIGN

Descriptive, secondary analysis of baseline data from two related lifestyle intervention trials.

SETTING

Clinical study open to civilian population through the Center for Translational Research on Inflammatory Diseases at the Veterans Affairs Medical Center in Houston, TX.

PARTICIPANTS

One hundred eight community-dwelling adults with obesity, aged 65 or older, recruited consecutively from two lifestyle intervention trials.

MEASUREMENTS

Cognition was assessed using Composite Age-Adjusted Scale Score from the National Institutes of Health Toolbox Cognition Battery: Obesity was assessed by body mass index (BMI) and also by truncal fat mas via dual energy x-ray absorptiometry. Frailty was assessed using the Physical Performance Test.

RESULTS

A significant linear regression model for cognition revealed frailty as the strongest predictor, followed by sex, and then truncal fat (R2=0.340, p<0.001).

CONCLUSION

Cognition among community-dwelling older adults with obese BMI may worsen with greater truncal fat mass. Frailty appears to be an important predictor of cognitive performance in this population.

Response to "A high lean body mass is not protecting from type 2 diabetes in the presence of a high body fat mass"

Sir, I have read with immense curiosity and enthusiasm the article 'A high lean body mass is not protecting from type 2 diabetes in the presence of a high body fat mass' by Simo K.J.Rehunen et al. [1]. It is a compactly written, engrossing article that contains a significant sample size. I applaud the authors for their sublime efforts.

Mass recovery following caloric restriction reverses lipolysis and proteolysis, but not gluconeogenesis, in insulin resistant OLETF rats

Caloric restriction (CR) is one of the most important behavioral interventions to reduce excessive abdominal adiposity, which is a risk factor for the development of insulin resistance. Previous metabolomics studies have characterized substrate metabolism during healthy conditions; however, the effects of CR and subsequent mass recovery on shifts in substrate metabolism during insulin resistance (IR) have not been widely investigated. To assess the effects of acute CR and the subsequent mass recovery on shifts in substrate metabolism, a cohort of 15-week old Long Evans Tokushima Otsuka (LETO) and Otsuka Long Evans Tokushima Fatty (OLETF) rats were calorie restricted (CR: 50% × 10 days) with or without partial body mass recovery (PR; 73% x 7 days), along with their respective ad libitum controls. End-of-study plasma samples were analyzed for primary carbon metabolites by gas chromatography (GC) time-of-flight (TOF) mass spectrometry (MS) data acquisition. Data analysis included PCA, Pearson correlation vs previously reported variables (adipose and body masses, and insulin resistance index, IRI), and metabolomics maps (MetaMapp) generated for the most significant group comparisons. All treatments elicited a significant group differentiation in at least one principal component. CR improved TCA cycle in OLETF, and increased lipolysis and proteolysis. These changes were reversed after PR except for gluconeogenesis. Plasma lipid concentrations were inversely correlated to IRI in LETO, but not OLETF. These shifts in substrate metabolism suggest that the CR-induced decreases in adipose may not be sufficient to more permanently alter substrate metabolism to improve IR status during metabolic syndrome.

Sarcopenia, frailty and type 2 diabetes mellitus (Review)

Skeletal muscle is the largest and most energy‑consuming organ in the human body, which plays an important role in energy metabolism and glucose uptake. There is a notable decrease in glucose uptake in the skeletal muscle of patients with type 2 diabetes mellitus (DM). Endurance exercise can reduce hyperglycemia and improve insulin resistance in patients with type 2 DM. Insulin exerts a variety of effects, many of which are mediated by Akt, including increasing glucose uptake, promoting glycogen synthesis and inhibiting glycogen degradation, increasing free fatty acid uptake, increasing protein synthesis, promoting muscle hypertrophy and inhibiting protein degradation. Skeletal muscle mass progressively declines with aging, resulting in loss of muscle strength and physical function. Sarcopenia is a syndrome characterized by loss of skeletal muscle mass and muscle weakness or loss of physical function, and frailty is another syndrome that has received great interest in recent years. Decreased organ function results in vulnerability to external stress. Frailty is associated with falls, fractures and hospitalization; however, there is the reversibility of returning to a healthy state with appropriate interventions. Frailty is classified into three subgroups: Physical frailty, social frailty and cognitive frailty, whereby sarcopenia is the main component of physical frailty. The present review discusses the associations between sarcopenia, frailty and type 2 DM based on current evidence.

Midlife and late-life diabetes and sarcopenia in a general older Japanese population: The Hisayama Study

AIMS/INTRODUCTION

To investigate the association between midlife or late-life diabetes and the development of sarcopenia in an older Japanese population.

MATERIALS AND METHODS

A total of 824 Japanese residents aged 65 to 84 years without sarcopenia were followed up from 2012 to 2017. Sarcopenia was determined following the Asian Working Group for Sarcopenia definition. The time of diabetes diagnosis was classified as midlife or late-life diabetes by the age at first diagnosis of diabetes (< 65 or ≥ 65 years) based on annual health checkups data over the past 24 years. The duration of diabetes was categorized into three groups of < 10, 10-15, and > 15 years. The odds ratios of incident sarcopenia according to the diabetic status were estimated using a logistic regression analysis.

RESULTS

During follow-up, 47 subjects developed sarcopenia. The multivariable-adjusted odds ratio for incident sarcopenia was significantly greater in subjects with diabetes at baseline than in those without it (odds ratio 2.51, 95% confidence interval 1.26-5.00). Subjects with midlife diabetes had a significantly greater risk of incident sarcopenia, whereas no significant association between late-life diabetes and incident sarcopenia was observed. With a longer duration of diabetes, the risk of incident sarcopenia increased significantly (P for trend = 0.002).

CONCLUSIONS

The present study suggests that midlife diabetes and a longer duration of diabetes are significant risk factors for incident sarcopenia in the older population. Preventing diabetes in midlife may reduce the risk of the development of sarcopenia in later life.

Prenatal air pollution exposure to diesel exhaust induces cardiometabolic disorders in adulthood in a sex-specific manner

BACKGROUND

Results from observational and experimental studies indicate that exposure to air pollutants during gestation reduces birth weight, whereas little is known on potential cardiometabolic consequences for the offspring at adulthood.

OBJECTIVES

Our aim was to evaluate the long-term effects of gestational exposure to diesel engine exhaust (DE) on adult offspring phenotype in a rabbit model.

METHODS

The protocol was designed to mimic human exposure in large European cities. Females rabbits were exposed to diluted (1 mg/m³) DE (exposed, n = 9) or clean air (controls, n = 7), from 3 days after mating, 2 h/d and 5 d/wk in a nose-only inhalation system throughout gestation (gestation days 3-27). After birth and weaning, 72 offspring (47 exposed and 25 controls) were raised until adulthood (7.5 months) to evaluate their cardio-metabolic status, including the monitoring of body weight and food intake, fasting biochemistry, body composition (iDXA), cardiovascular parameters and glucose tolerance. After a metabolic challenge (high fat diet in males and gestation in females), animals were euthanized for postmortem phenotyping.

RESULTS

Sex-specific responses to maternal exposure were observed in adult offspring. Age-related increases in blood pressure (p = 0.058), glycaemia (p = 0.029), and perirenal fat mass (p = 0.026) as well as reductions in HDL-cholesterol (p = 0.025) and fat-to-body weight ratio (p = 0.011) were observed in exposed males, suggesting a metabolic syndrome. Almost only trends were observed in exposed females with higher triglycerides and decreased bone density compared to control females. Metabolic challenges triggered or amplified some biological responses, especially in females.

CONCLUSIONS

In utero exposure to air pollution predisposed rabbit offspring to cardiometabolic disorders in a sex-specific manner.

Transcriptomic links to muscle mass loss and declines in cumulative muscle protein synthesis during short-term disuse in healthy younger humans

Muscle disuse leads to a rapid decline in muscle mass, with reduced muscle protein synthesis (MPS) considered the primary physiological mechanism. Here, we employed a systems biology approach to uncover molecular networks and key molecular candidates that quantitatively link to the degree of muscle atrophy and/or extent of decline in MPS during short-term disuse in humans. After consuming a bolus dose of deuterium oxide (D₂ O; 3 mL.kg^-1 ), eight healthy males (22 ± 2 years) underwent 4 days of unilateral lower-limb immobilization. Bilateral muscle biopsies were obtained post-intervention for RNA sequencing and D₂ O-derived measurement of MPS, with thigh lean mass quantified using dual-energy X-ray absorptiometry. Application of weighted gene co-expression network analysis identified 15 distinct gene clusters ("modules") with an expression profile regulated by disuse and/or quantitatively connected to disuse-induced muscle mass or MPS changes. Module scans for candidate targets established an experimentally tractable set of candidate regulatory molecules (242 hub genes, 31 transcriptional regulators) associated with disuse-induced maladaptation, many themselves potently tied to disuse-induced reductions in muscle mass and/or MPS and, therefore, strong physiologically relevant candidates. Notably, we implicate a putative role for muscle protein breakdown-related molecular networks in impairing MPS during short-term disuse, and further establish DEPTOR (a potent mTOR inhibitor) as a critical mechanistic candidate of disuse driven MPS suppression in humans. Overall, these findings offer a strong benchmark for accelerating mechanistic understanding of short-term muscle disuse atrophy that may help expedite development of therapeutic interventions.

Low Protein Intakes and Poor Diet Quality Associate with Functional Limitations in US Adults with Diabetes: A 2005-2016 NHANES Analysis

Type 2 diabetes is associated with an increased risk for sarcopenia. Moreover, sarcopenia correlates with increased risk for falls, fractures, and mortality. This study aimed to explore relationships among nutrient intakes, diet quality, and functional limitations in a sample of adults across levels of glycemic control. Data were examined from 23,487 non-institutionalized adults, 31 years and older, from the 2005-2016 National Health and Nutrition Examination Survey. Hemoglobin A1c (%) was used to classify level of glycemic control: non-diabetes (<5.7%); pre-diabetes (5.7-6.4%); diabetes (≥6.5%). Dietary data were collected from a single 24-h dietary recall. Participants were categorized as meeting or below the protein recommendation of 0.8 g/kg of body weight. Physical functioning was assessed across 19-discrete physical tasks. Adults below the protein recommendation consumed significantly more carbohydrate and had lower diet quality across all glycemic groups compared to those who met the protein recommendation (p < 0.001). Adults with diabetes who did not meet protein recommendations had significantly poorer diet quality and significantly higher mean number of functional limitations. A greater percent of adults with diabetes who did not meet the protein recommendation reported being physically limited for most activities, with more than half (52%) reporting limitations for stooping, crouching, and kneeling. This study underscores the potential for physical limitations associated with low protein intakes, especially in adults with diabetes. In the longer term, low protein intakes may result in increased risk of muscle loss, as protein intake is a critical nutritional factor for prevention of sarcopenia, functional limitations, and falls.

Correlation between plasma ZAG and adiponectin in older adults: gender modification and frailty specificity

Background

Adiponectin and zinc alpha2-glycoprotein (ZAG) are associated with frailty. This study aims to further examine the association of adiponectin with ZAG.

Methods

Outpatients aged 65 years or older with chronic disease followed up in a hospital-based program were recruited for a comprehensive geriatric assessment. We excluded outpatients who were bedridden, residing in a nursing home, with expected life expectancy less than 6 months, or with severe hearing or communication impairment. Plasma ZAG and adiponectin levels were measured. Association between plasma ZAG and adiponectin levels was analyzed by univariate and multivariable linear regression analyses.

Results

A total of 189 older adults were enrolled (91 men and 98 women, mean age: 77.2 ± 6.1 years). Log-transformed plasma ZAG level was 1.82 ± 0.11 μg/mL, and it was significantly higher in men than that in women (1.85 ± 0.12 vs 1.79 ± 0.10 μg/mL, P = .0006). Log-transformed plasma adiponectin level was 1.00 ± 0.26 μg/mL, and there was no significant gender difference (P = .195). Overall, plasma ZAG level positively correlated with plasma adiponectin level in the multivariable linear regression analysis (P = .0085). The gender-specific significance, however, was less clear: this relationship was significant in men (P = .0049) but not in women (P = .2072). To be more specific by frailty phenotype components, plasma adiponectin was positively correlated with weight loss (P = .0454) and weakness (P = .0451).

Conclusions

Both of ZAG and adiponectin may be potential frailty biomarkers. Plasma ZAG is an independent factor of plasma adiponectin, especially in older male adults.

Relationship of Multimorbidity, Obesity Status, and Grip Strength among Older Adults in Taiwan

Background: The combination of multiple disease statuses, muscle weakness, and sarcopenia among older adults is an important public health concern, and a health burden worldwide. This study evaluates the association between chronic disease statuses, obesity, and grip strength (GS) among older adults in Taiwan. Methods: A community-based survey was conducted every 3 years among older adults over age 65, living in Chiayi County, Taiwan. Demographic data and several diseases statuses, such as diabetes mellitus, hypertension, cerebrovascular disease, cardiovascular disease, and certain cancers, were collected using a questionnaire. Anthropometric characteristics were measured using standard methods. Grip strength was measured using a digital dynamometer (TKK5101) method. Results: A total of 3739 older individuals were recruited (1600 males and 2139 females) with the mean age of 72.9 years. The mean GS was 32.8 ± 7.1 kg for males and 21.6 ± 4.8 kg for females. GS significantly decreased most in males with cerebrovascular disease (from 33.0—29.5 kg, p < 0.001) and in females with diabetes mellitus (from 21.8—21.0 kg, p < 0.01). GS was highest in older adults with obesity (body mass index ≥ 27 kg/m²); however, there was no significant change of GS as the disease number increased. Conclusion: Older adults who have two, rather than one or greater than three chronic diseases, have significantly lower GSs than those who are healthy. Stroke and CKD for males, and hypertension and diabetes for females, are important chronic diseases that are significantly associated with GS. Furthermore, being overweight may be a protective factor for GS in older adults of both sexes.

Dual effects of insulin resistance on mortality and function in non-diabetic older adults: findings from the Toledo Study of Healthy Aging

Insulin signalling declines with increasing age and impacts skeletal muscle function and longevity in animal models. Our aim was to assess the relationships between insulin resistance (IR) and frailty and mortality in a unique community-dwelling cohort of older people. 991 non-diabetic subjects from the Toledo Study of Healthy Ageing (TSHA) cohort were included. IR was estimated by the homeostasis model assessment index (HOMA-IR) at baseline while frailty was determined by frailty phenotype (FP) and Frailty Trait Scale (FTS) at baseline and after 5-year follow-up. Deaths were also determined. Multivariate regression models were used to analyze the effects of HOMA-IR on outcomes. Age, gender, BMI, education level, cardio- and cerebro-vascular disease, glomerular filtration rate, and disability were included as potential confounding variables in progressive adjustment models. IR determined as increasing log HOMA-IR was inversely associated with risk of mortality. The association remained significant for all adjustment models (HR: 0.64-0.69). When we analyzed survival curves, the higher the HOMA-IR tertile, the lower the mortality rate (highest vs lowest tertile, p = 0.0082). In contrast, IR increased the risk of incident frailty determined by FP (OR 1.81 [1.14-2.87]) as well as deterioration of frailty status determined by worsening in FTS score (OR 1.28 [1.01-1.63]) at 5-year follow-up. In non-diabetic older subjects, IR significantly increases the risk for frailty and functional decline but decreased the risk of death at 5-year follow-up. This finding raises the need of assessing the effect of biomarkers on different outcomes before establishing their role as biomarkers of aging.

Presence and Implications of Sarcopenia in Non-alcoholic Steatohepatitis

Sarcopenia, defined as the loss of muscle strength, mass, and functionality, confers a poor prognosis in the setting of cirrhosis. Given its clinical significance, a better understanding of the underlying mechanisms leading to cirrhosis, sarcopenia, and their co-occurrence may improve these patients' outcomes. Non-alcoholic steatohepatitis (NASH) shares many of the same etiologies as sarcopenia, including insulin resistance, chronic inflammation, and ectopic adipocyte deposition, which are hallmarks of metabolic syndrome (MS). NASH thus serves as a prime candidate for further exploration into the underlying pathophysiology and relationship between these three conditions. In this review, we discuss the natural history of NASH and sarcopenia, explore the interplay between these conditions in the scope of MS, and seek to better define how an assessment of muscle mass, strength, and functionality in this population is key to improved diagnosis and management of patients with sarcopenia and NASH.

Tail suspension is useful as a sarcopenia model in rats

Background

Sarcopenia promotes skeletal muscle atrophy and exhibits a high mortality rate. Its elucidation is of the highest clinical importance, but an animal experimental model remains controversial. In this study, we investigated a simple method for studying sarcopenia in rats.

Results

Muscle atrophy was investigated in 24-week-old, male, tail-suspended (TS), Sprague Dawley and spontaneously hypertensive rats (SHR). Age-matched SD rats were used as a control group. The skeletal muscle mass weight, muscle contraction, whole body tension (WBT), cross-sectional area (CSA), and Muscle RING finger-1 (MuRF-1) were assessed. Enzyme-linked immunosorbent assay was used to evaluate the MuRF-1 levels. Two muscles, the extensor digitorum longus and soleus muscles, were selected for representing fast and slow muscles, respectively. All data, except CSA, were analyzed by a one-way analysis of variance, whereas CSA was analyzed using the Kruskal-Wallis test.

Muscle mass weight, muscle contraction, WBT, and CSA were significantly lower in the SHR (n = 7) and TS (n = 7) groups than in the control group, whereas MuRF-1 expression was dominant.

Conclusions

TS and SHR presented sarcopenic phenotypes in terms of muscle mass, muscle contraction and CSA. TS is a useful technique for providing muscle mass atrophy and weakness in an experimental model of sarcopenia in rats.

Decrease in Serum Urate Level Is Associated With Loss of Visceral Fat in Male Gout Patients

OBJECTIVE

To clarify the relationship between serum urate (SU) decrease and visceral fat area (VFA) reduction in patients with gout.

METHODS

We retrospectively analyzed 237 male gout patients who had two sets of body composition and metabolic measurements within 6 months. Subjects included had all been treated with urate-lowering therapy (ULT) (febuxostat 20-80 mg/day or benzbromarone 25-50 mg/day, validated by the medical record). All patients were from the specialty gout clinic of The Affiliated Hospital of Qingdao University. The multiple linear regression model evaluated the relationship between change in SU [ΔSU, (baseline SU) - (final visit SU)] and change in VFA [ΔVFA, (baseline VFA) - (final visit VFA)].

RESULTS

ULT resulted in a mean (standard deviation) decrease in SU level (464.22 ± 110.21 μmol/L at baseline, 360.93 ± 91.66 μmol/L at the final visit, p <0.001) accompanied by a decrease in median (interquartile range) VFA [97.30 (81.15-118.55) at baseline, 90.90 (75.85-110.05) at the final visit, p < 0.001]. By multiple regression model, ΔSU was identified to be a significant determinant variable of decrease in VFA (beta, 0.302; p = 0.001).

CONCLUSIONS

The decrease in SU level is positively associated with reduced VFA. This finding provides a rationale for clinical trials to affirm whether ULT promotes loss of visceral fat in patients with gout.

Muscle Size and Strength of the Lower Body in Supervised and in Combined Supervised and Unsupervised Low-Load Resistance Training

This study aimed to clarify whether low-load resistance training at a low frequency (twice a week) using body weight and elastic band improves muscle size, muscle strength, and physical functions and to compare the training effects between supervised training and a combination of supervised and unsupervised training in untrained older adults. Fifty-one older adults (ages: 57-75 years) selected to either a supervised (S) training group (n = 34) or a combined supervised and unsupervised (SU) group (n = 17). Both groups performed low-load resistance training composed of nine exercises for 12 weeks. The S group participated in supervised exercise sessions twice a week, and the SU group performed a supervised exercise session once a week and an unsupervised exercise session at home also once a week. For muscle thicknesses in the anterior aspects of the forearm, upper arm, and thigh and the posterior aspect of the thigh, group × time interactions were observed (p < 0.05). The hypertrophic effects were higher in the S group. Isometric knee extension strength and physical functions increased similarly in both groups. Low-load resistance training using body weight and elastic band twice a week for 12 weeks induces muscle hypertrophy and increases muscle strength and physical functions in older adults. Although the muscle hypertrophic effects are greater in the S group than in the SU group, the other effects were similar between the groups.

Cross-sectional and Prospective Associations of Rest-Activity Rhythms With Metabolic Markers and Type 2 Diabetes in Older Men

OBJECTIVE

Disruption of rest-activity rhythms is cross-sectionally associated with metabolic disorders, including type 2 diabetes, yet it remains unclear whether it predicts impaired glucose metabolism and homeostasis. The aim of this study is to examine the cross-sectional and prospective associations between rest-activity rhythm characteristics and glycemic measures in a cohort of older men.

RESEARCH DESIGN AND METHODS

Baseline rest-activity rhythms were derived from actigraphy with use of extended cosine model analysis. With subjects fasting, glucose, insulin, and HOMA of insulin resistance (HOMA-IR) were measured from blood at baseline and after ∼3.5 years. Type 2 diabetes was defined based on self-report, medication use, and fasting glucose.

RESULTS

In the cross-sectional analysis (n = 2,450), lower 24-h amplitude-to-mesor ratio (i.e., mean activity-adjusted rhythm amplitude) and reduced overall rhythmicity were associated with higher fasting insulin and HOMA-IR (all P _trend < 0.0001), indicating increased insulin resistance. The odds of baseline type 2 diabetes were significantly higher among those in the lowest quartile of amplitude (Q1) (odds ratio [OR]_{Q1 vs. Q4} 1.63 [95% CI 1.14, 2.30]) and late acrophase group (OR_{late vs. normal} 1.46 [95% CI 1.04, 2.04]). In the prospective analysis (n = 861), multiple rest-activity characteristics predicted a two- to threefold increase in type 2 diabetes risk, including a lower amplitude (OR_{Q1 vs. Q4} 3.81 [95% CI 1.45, 10.00]) and amplitude-to-mesor ratio (OR 2.79 [95% CI 1.10, 7.07]), reduced overall rhythmicity (OR 3.49 [95% CI 1.34, 9.10]), and a late acrophase (OR 2.44 [1.09, 5.47]).

CONCLUSIONS

Rest-activity rhythm characteristics are associated with impaired glycemic metabolism and homeostasis and higher risk of incident type 2 diabetes.

Sarkopenie im Kontext von Insulinresistenz und Diabetes mellitus im Alter – Daten aus der Berliner Altersstudie II

Hintergrund Diabetes mellitus Typ 2 (T2DM) und Sarkopenie nehmen mit steigendem Alter in ihrer Prävalenz zu und können langfristig betrachtet jeweils zu erheblichen gesundheitlichen und funktionellen Einschränkungen führen. Während eine zunehmende Insulinresistenz bei abnehmender Muskelmasse plausibel erscheint, sind umgekehrt auch glukotoxische negative Effekte auf die Skelettmuskulatur im Sinne einer sekundären Sarkopenie denkbar. Ziel dieser Arbeit war es, den Zusammenhang zwischen Sarkopenie, Insulinresistenz und T2DM bei älteren Menschen zu untersuchen.

Methoden Untersucht wurden 1555 Probanden der Berliner Altersstudie II (BASE-II) mit einem durchschnittlichen Alter von 68 ± 4 Jahren. Die Diagnose T2DM wurde basierend auf der Anamnese sowie oralem Glukosetoleranztest und HbA1c-Wert nach ADA-Kriterien gestellt und die Insulinresistenz wurde via Homeostatic Model Assessment for Insulin resistance (HOMA-IR) und Insulinsensitivitätsindex nach Matsuda (ISI) eingeschätzt. Die appendikuläre Skelettmuskelmasse (ALM) wurde mittels Dual-Röntgen-Absorptiometrie (DXA) und eine Sarkopenie mithilfe der anhand des Body-Mass-Index (BMI) korrigierten Muskelmasse (ALM/BMI) nach den Cut-off-Werten des FNIH Sarcopenia Project bestimmt. Gruppenvergleiche wurden mittels Kruskal-Wallis-Test berechnet, und der Zusammenhang zwischen Diabetes mellitus und Sarkopenie bzw. ALM und Insulinresistenz wurde mittels geeigneter Regressionsmodelle überprüft.

Ergebnisse 25,2 % der insgesamt 160 Probanden mit T2DM hatten bereits eine Sarkopenie. Sarkopenisch-adipöse Probanden wiesen im Vergleich zu nur adipösen, nur sarkopenen oder weder adipösen noch sarkopenen Probanden im Median einen niedrigeren ISI und einen höheren HOMA-IR auf (jeweils p < 0,001). T2DM zeigte sich unabhängig assoziiert mit Sarkopenie (OR 3,293, 95 %-KI 1,984–5,466, p < 0,001), während nach Ausschluss bekannter Diabetiker eine höhere ALM mit einem höheren ISI (B 0,229, 95 %-KI 0,119–0,338; p < 0,001), nicht jedoch niedrigerem HOMA-IR (B –0,017, 95 %-KI –0,089–0,055; p = 0,640) einherging.

Diskussion Sarkopenie ist sowohl mit Insulinresistenz als auch T2DM assoziiert. Die Frage bzgl. der Kausalität ist aufgrund des querschnittlichen Designs der Studie nicht zu beantworten, jedoch sollte eine mögliche Rolle des T2DM als sekundäre Sarkopenieursache berücksichtigt und weiter untersucht werden. Im Hinblick auf mögliche Folgen erscheinen die Identifizierung von Risikopatienten mit kombiniertem Auftreten von Sarkopenie und Insulinresistenz und die Evaluation basaler präventiver Maßnahmen wie gezieltes körperliches Training und angepasste Ernährung ein weiterführendes sinnvolles Ziel.

Acute rimonabant treatment promotes protein synthesis in C2C12 myotubes through a CB1-independent mechanism

Sarcopenia is an age-related loss of muscle mass associated with changes in skeletal muscle protein homeostasis due to lipid accumulation and anabolic resistance; changes that are also commonly described in obesity. Activation of the endocannabinoid system is associated with the development of obesity and insulin resistance, and with the perturbed skeletal muscle development. Taken together this suggests that endocannabinoids could be regulators of skeletal muscle protein homeostasis. Here we report that rimonabant, an antagonist for the CB1 receptor, can prevent dexamethasone-induced C2C12 myotube atrophy without affecting the mRNA expression of atrogin-1/MAFbx (a marker of proteolysis), which suggests it is involved in the control of protein synthesis. Rimonabant alone stimulates protein synthesis in a time- and dose-dependent manner through mTOR- and intracellular calcium-dependent mechanisms. CB1 agonists are unable to modulate protein synthesis or prevent the effect of rimonabant. Using C2C12 cells stably expressing an shRNA directed against CB1, or HEK293 cells overexpressing HA-tagged CB1, we demonstrated that the effect of rimonabant is unaffected by CB1 expression level. In summary, rimonabant can stimulate protein synthesis in C2C12 myotubes through a CB1-independent mechanism. These results highlight the need to identify non-CB1 receptor(s) mediating the pro-anabolic effect of rimonabant as potential targets for the treatment of sarcopenia, and to design new side-effect-free molecules that consolidate the effect of rimonabant on skeletal muscle protein synthesis.

Weight change and risk of the foundation of National Institute of Health Sarcopenia-defined low lean mass: Data from the National Health and Nutrition examination surveys 1999-2004

BACKGROUND

Self-reported weight change may lead to adverse outcomes. We evaluated weight change with cutpoints of low lean mass (LLM) in older adults.

METHODS

Of 4984 subjects ≥60 years from NHANES 1999-2004, we applied LLM cutoffs of appendicular lean mass (ALM):body mass index (BMI) males<0.789, females<0.512. Self-reported weight was assessed at time of survey, and questions asked participants their weight one and 10 years earlier, and at age 25. Weight changes were categorized as greater/less/none than 5%. Logistic regression assessed weight change (gain, loss, no change) on LLM, after adjustment.

RESULTS

Of 4984 participants (56.5% female), mean age and BMI were 71.1 years and 28.2 kg/m2. Mean ALM was 19.7 kg. In those with LLM, 13.5% and 16.3% gained/lost weight in the past year, while 48.9% and 19.4% gained/lost weight in the past decade. Compared to weight at age 25, 85.2 and 6.1% of LLM participants gained and lost ≥5% of their weight, respectively. Weight gain over the past year was associated with a higher risk of LLM (OR 1.35 [0.99,1.87]) compared to weight loss ≥5% over the past year (0.89 [0.70,1.12]). Weight gain (≥5%) over 10-years was associated with a higher risk of LLM (OR 2.03 [1.66, 2.49]) while weight loss (≥5%) was associated with a lower risk (OR 0.98 [0.76,1.28]). Results were robust compared to weight at 25 years (gain OR 2.37 [1.76,3.20]; loss OR 0.95 [0.65,1.39]).

CONCLUSION

Self-reported weight gain suggests an increased risk of LLM. Future studies need to verify the relationship with physical function.

Impact of Protein Intake in Older Adults with Sarcopenia and Obesity: A Gut Microbiota Perspective

The continuous population increase of older adults with metabolic diseases may contribute to increased prevalence of sarcopenia and obesity and requires advocacy of optimal nutrition treatments to combat their deleterious outcomes. Sarcopenic obesity, characterized by age-induced skeletal-muscle atrophy and increased adiposity, may accelerate functional decline and increase the risk of disability and mortality. In this review, we explore the influence of dietary protein on the gut microbiome and its impact on sarcopenia and obesity. Given the associations between red meat proteins and altered gut microbiota, a combination of plant and animal-based proteins are deemed favorable for gut microbiota eubiosis and muscle-protein synthesis. Additionally, high-protein diets with elevated essential amino-acid concentrations, alongside increased dietary fiber intake, may promote gut microbiota eubiosis, given the metabolic effects derived from short-chain fatty-acid and branched-chain fatty-acid production. In conclusion, a greater abundance of specific gut bacteria associated with increased satiation, protein synthesis, and overall metabolic health may be driven by protein and fiber consumption. This could counteract the development of sarcopenia and obesity and, therefore, represent a novel approach for dietary recommendations based on the gut microbiota profile. However, more human trials utilizing advanced metabolomic techniques to investigate the microbiome and its relationship with macronutrient intake, especially protein, are warranted.

Metabolic alterations in spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA) is a rare, X-linked neuromuscular disease characterised by lower motor neurons degeneration, slowly progressive myopathy and multisystem involvement. SBMA is caused by trinucleotide repeat expansion in the first exon of the androgen receptor (AR) gene on chromosome X that encodes a polyglutamine (polyQ) tract in the AR protein. Disease onset occurs between 30-60 years of age with easy fatigability, muscle cramps, and weakness in the limbs. In addition to neuromuscular involvement, in SBMA phenotype, many non-neural manifestations are present. Recently, some studies have reported a high prevalence of metabolic and liver disorders in patients with SBMA. Particularly, fatty liver and insulin resistance (IR) have been found in many SBMA patients. The alteration of AR function and the androgen insensitivity can be involved in both fatty liver and IR. In turn, IR and liver alterations can influence neuromuscular damage through different mechanisms. These data lead to consider SBMA as a metabolic as well as a neuromuscular disease. The mechanism of metabolic alterations, their link with the neuromuscular damage, the effects on the course of disease and their treatment will have to be yet fully clarified.