Muscle protein anabolism in type 2 diabetes

Are strategies to increase muscle mass and strength as effective in people with type 2 diabetes?

People with type 2 diabetes (T2D) have a 2-3-time higher risk of developing sarcopenia, a musculoskeletal disease marked by a progressive loss of skeletal muscle mass and strength, compared to people without T2D. This narrative review examines the effectiveness of lifestyle interventions in enhancing muscle mass and strength in people with T2D, emphasizing their growing importance with advancements in obesity treatments. PubMed and Google Scholar were utilized to identify the most relevant published studies based on the authors' knowledge. The maintenance of skeletal muscle strength and mass in people with T2D is becoming more prominent due to the advent of weight loss therapies such as low-energy diets, bariatric surgery and pharmacotherapies. Although the weight loss is to be commended, a large proportion (20-50%) of the weight loss comes from lean mass, indicative of a loss in muscle mass. There are currently no pharmacotherapies to increase, or mitigate the loss of, lean mass, with lifestyle strategies prominent in this arena. Resistance exercise is the most effective method to increase muscle mass and strength in people with T2D, but there is some evidence of an anabolic resistance. Aerobic exercise and increased dietary protein intake may result in small increases in muscle mass and strength, with no evidence of an anabolic resistance to these stimuli. Exercise and protein supplementation can increase, or aid in the retention of, muscle strength and mass in individuals with T2D, but further research is needed to explore their benefits in patients undergoing concomitant pharmaceutical and surgical treatments.

Loss or inhibition of lysosomal acid lipase in vitro leads to cholesteryl ester accumulation without affecting muscle formation or mitochondrial function

Skeletal muscle (SM) is essential for movement, stability, and overall body function, and it readily adapts to changes in energy demand. Myogenesis is energy-intensive and involves complex molecular and cellular events. We recently demonstrated that the absence of lysosomal acid lipase (LAL) in vivo significantly impacts the SM phenotype, primarily by disrupting energy homeostasis and reducing ATP production. As systemic LAL deficiency affects multiple organs, we hypothesized that the altered SM phenotype resulted from systemic rather than SM-specific loss of LAL activity. To distinguish between systemic and cell-intrinsic effects, we used primary myoblasts isolated from Lal-deficient (-/-) mice as well as C2C12 cells treated with the pharmacological inhibitor of LAL, Lalistat-2. We found a significant accumulation of cholesteryl esters in both models studied, highlighting the central role of LAL in lipid catabolism in the SM. However, lipid accumulation was absent under lipoprotein-deficient culture conditions. Neither genetic loss nor pharmacological inhibition of LAL affected myofiber formation or mitochondrial function in vitro, in contrast to what we observed in SM isolated from Lal-/- mice. Tracing [13C6]-labeled glucose in both cell culture models revealed only minor changes in tricarboxylic acid cycle metabolites. These results suggest that although LAL plays an essential role in lipid metabolism, its impact on the processes involved in muscle differentiation and cellular energy production is minor. We conclude that the cell-intrinsic effects of Lal-/- SM are unlikely to drive the SM phenotype observed in vivo.

Differential seasonal performance of C3-epi-D3 level and proportion on multiple metabolic disorders in patients with type 2 diabetes mellitus

BACKGROUND AND AIM

Recent Mendelian randomization and meta analysis suggest a controversial causality between C3-epimer of 25 hydroxyvitamin D3 (C3-epi-D3) and type 2 diabetes mellitus (T2DM). The clinical evidence regarding the impact of C3-epi-D3 on the progression of T2DM is currently insufficient. This study aims to investigate whether C3-epi-D3 has any effect on metabolic disorders of T2DM patients.

METHODS

A total of 1222 patients with T2DM were prospectively enrolled in this study and followed up every 1 to 2 months for 3 to 6 months. Kidney biomarkers, lipids, electrolytes, and 25 hydroxyvitamin D (25-OHD) metabolites were measured as required during follow-up, to investigate the association of C3-epi-D3 levels and %C3-epi-D3 with metabolic disorders, including dyslipidemia, chronic kidney disease (CKD), and calcium-phosphorus metabolic disorder.

RESULTS

Among these T2DM patients, there were age and seasonal differences in C3-epi-D3 levels (χ2 = 10.419 and 19.609, P = 0.034 and < 0.001), but only seasonal difference in %C3-epi-D3 (χ2 = 79.299, P < 0.001). C3-epi-D3 levels showed an evident correlation with calcium-phosphorus product during autumn and winter (ρ = - 0.336 and - 0.304, both P < 0.001), and was confirmed as an independent factor on calcium-phosphorus metabolic disorder during autumn and winter by subsequent partial correlation analysis (rpartial = - 0.300 and - 0.319, both P < 0.001). Both C3-epi-D3 levels and %C3-epi-D3 showed evident correlation with the severity of chronic kidney disease (CKD) in summer (ρ = 0.344 and 0.445, both P < 0.001). But subsequent multinomial logistic regression confirmed that only %C3-epi-D3 independently associated with moderate CKD severity in summer (OR = 1.348, P < 0.001), as well as serious CKD severity in spring, summer, and autumn (OR = 1.324, 1.342, and 1.698, all P < 0.001). Additionally, no evident correlation was observed between C3-epi-D3 and dyslipidemia.

CONCLUSION

Our study releases a seasonally differential impact of C3-epi-D3 levels and proportions on metabolic disorders of T2DM patients, considering to be potentially related to their pathogenesis of different metabolic disorders. The independent association between %C3-epi-D3 and CKD suggests a potential pathological relevance involving C3-epi-D3 itself.

Impaired skeletal muscle regeneration in diabetes: From cellular and molecular mechanisms to novel treatments

Diabetes represents a major public health concern with a considerable impact on human life and healthcare expenditures. It is now well established that diabetes is characterized by a severe skeletal muscle pathology that limits functional capacity and quality of life. Increasing evidence indicates that diabetes is also one of the most prevalent disorders characterized by impaired skeletal muscle regeneration, yet underlying mechanisms and therapeutic treatments remain poorly established. In this review, we describe the cellular and molecular alterations currently known to occur during skeletal muscle regeneration in people with diabetes and animal models of diabetes, including its associated comorbidities, e.g., obesity, hyperinsulinemia, and insulin resistance. We describe the role of myogenic and non-myogenic cell types on muscle regeneration in conditions with or without diabetes. Therapies for skeletal muscle regeneration and gaps in our knowledge are also discussed, while proposing future directions for the field.

Ketogenic diet preserves muscle mass and strength in a mouse model of type 2 diabetes

Diabetes is often associated with reduced muscle mass and function. The ketogenic diet (KD) may improve muscle mass and function via the induction of nutritional ketosis. To test whether the KD is able to preserve muscle mass and strength in a mouse model of type 2 diabetes (T2DM), C57BL/6J mice were assigned to lean control, diabetes control, and KD groups. The mice were fed a standard diet (10% kcal from fat) or a high-fat diet (HFD) (60% kcal from fat). The diabetic condition was induced by a single injection of streptozotocin (STZ; 100 mg/kg) and nicotinamide (NAM; 120 mg/kg) into HFD-fed mice. After 8-week HFD feeding, the KD (90% kcal from fat) was fed to the KD group for the following 6 weeks. After the 14-week experimental period, an oral glucose tolerance test and grip strength test were conducted. Type 2 diabetic condition induced by HFD feeding and STZ/NAM injection resulted in reduced muscle mass and grip strength, and smaller muscle fiber areas. The KD nutritional intervention improved these effects. Additionally, the KD altered the gene expression of nucleotide-binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome- and endoplasmic reticulum (ER) stress-related markers in the muscles of diabetic mice. Collectively, KD improved muscle mass and function with alterations in NLRP3 inflammasome and ER stress.

Blockade of glucagon increases muscle mass and alters fiber type composition in mice deficient in proglucagon-derived peptides

AIMS/INTRODUCTION

Glucagon is secreted from pancreatic α-cells and plays an important role in amino acid metabolism in liver. Various animal models deficient in glucagon action show hyper-amino acidemia and α-cell hyperplasia, indicating that glucagon contributes to feedback regulation between the liver and the α-cells. In addition, both insulin and various amino acids, including branched-chain amino acids and alanine, participate in protein synthesis in skeletal muscle. However, the effect of hyperaminoacidemia on skeletal muscle has not been investigated. In the present study, we examined the effect of blockade of glucagon action on skeletal muscle using mice deficient in proglucagon-derived peptides (GCGKO mice).

MATERIALS AND METHODS

Muscles isolated from GCGKO and control mice were analyzed for their morphology, gene expression and metabolites.

RESULTS

GCGKO mice showed muscle fiber hypertrophy, and a decreased ratio of type IIA and an increased ratio of type IIB fibers in the tibialis anterior. The expression levels of myosin heavy chain (Myh) 7, 2, 1 and myoglobin messenger ribonucleic acid were significantly lower in GCGKO mice than those in control mice in the tibialis anterior. GCGKO mice showed a significantly higher concentration of arginine, asparagine, serine and threonine in the quadriceps femoris muscles, and also alanine, aspartic acid, cysteine, glutamine, glycine and lysine, as well as four amino acids in gastrocnemius muscles.

CONCLUSIONS

These results show that hyperaminoacidemia induced by blockade of glucagon action in mice increases skeletal muscle weight and stimulates slow-to-fast transition in type II fibers of skeletal muscle, mimicking the phenotype of a high-protein diet.

Exercise in the Prevention and Treatment of Type 2 Diabetes

Type 2 diabetes is a systemic, multifactorial disease that is a leading cause of morbidity and mortality globally. Despite a rise in the number of available medications and treatments available for management, exercise remains a first-line prevention and intervention strategy due to established safety, efficacy, and tolerability in the general population. Herein we review the predisposing risk factors for, prevention, pathophysiology, and treatment of type 2 diabetes. We emphasize key cellular and molecular adaptive processes that provide insight into our evolving understanding of how, when, and what types of exercise may improve glycemic control. © 2023 American Physiological Society. Compr Physiol 13:1-27, 2023.

Mesenchymal stromal cells ameliorate diabetes-induced muscle atrophy through exosomes by enhancing AMPK/ULK1-mediated autophagy

BACKGROUND

Diabetes and obesity are associated with muscle atrophy that reduces life quality and lacks effective treatment. Mesenchymal stromal cell (MSC)-based therapy can ameliorate high fat-diet (HFD) and immobilization (IM)-induced muscle atrophy in mice. However, the effect of MSCs on muscle atrophy in type 2 diabetes mellitus (T2DM) and the potential mechanism is unclear. Here, we evaluated the efficacy and explored molecular mechanisms of human umbilical cord MSCs (hucMSCs) and hucMSC-derived exosomes (MSC-EXO) on diabetes- and obesity-induced muscle atrophy.

METHODS

Diabetic db/db mice, mice fed with high-fat diet (HFD), mice with hindlimb immobilization (IM), and C2C12 myotubes were used to explore the effect of hucMSCs or MSC-EXO in alleviating muscle atrophy. Grip strength test and treadmill running were used to measure skeletal muscle strength and performance. Body composition, muscle weight, and muscle fibre cross-sectional area (CSA) was used to evaluate muscle mass. RNA-seq analysis of tibialis anterior (TA) muscle and Western blot analysis of muscle atrophy signalling, including MuRF1 and Atrogin 1, were performed to investigate the underlying mechanisms.

RESULTS

hucMSCs increased grip strength (P = 0.0256 in db/db mice, P = 0.012 in HFD mice, P = 0.0097 in IM mice), running endurance (P = 0.0154 in HFD mice, P = 0.0006 in IM mice), and muscle mass (P = 0.0004 in db/db mice, P = 0.0076 in HFD mice, P = 0.0144 in IM mice) in all models tested, with elevated CSA of muscle fibres (P < 0.0001 in db/db mice and HFD mice, P = 0.0088 in IM mice) and reduced Atrogin1 (P = 0.0459 in db/db mice, P = 0.0088 in HFD mice, P = 0.0016 in IM mice) and MuRF1 expression (P = 0.0004 in db/db mice, P = 0.0077 in HFD mice, P = 0.0451 in IM mice). MSC-EXO replicated all these hucMSC-mediated changes (P = 0.0103 for grip strength, P = 0.013 for muscle mass, P < 0.0001 for CSA of muscle fibres, P = 0.0171 for Atrogin1 expression, and P = 0.006 for MuRF1 expression). RNA-seq revealed that hucMSCs activated the AMPK/ULK1 signalling and enhanced autophagy. Knockdown of AMPK or inhibition of autophagy with 3-methyladenine (3-MA) diminished the beneficial anti-atrophy effects of hucMSCs or MSC-EXO.

CONCLUSIONS

Our results suggest that human umbilical cord mesenchymal stromal cells mitigate diabetes- and obesity-induced muscle atrophy via enhancing AMPK/ULK1-mediated autophagy through exosomes, with implications of applying hucMSCs or hucMSC-derived exosomes to treat muscle atrophy.

Functional constituents of plant-based foods boost immunity against acute and chronic disorders

Plant-based foods are becoming an increasingly frequent topic of discussion, both scientific and social, due to the dissemination of information and exchange of experiences in the media. Plant-based diets are considered beneficial for human health due to the supply of many valuable nutrients, including health-promoting compounds. Replacing meat-based foods with plant-based products will provide many valuable compounds, including antioxidants, phenolic compounds, fibers, vitamins, minerals, and some ω3 fatty acids. Due to their high nutritional and functional composition, plant-based foods are beneficial in acute and chronic diseases. This article attempts to review the literature to present the most important data on nutrients of plant-based foods that can then help in the prevention of many diseases, such as different infections, such as coronavirus disease, pneumonia, common cold and flu, asthma, and bacterial diseases, such as bronchitis. A properly structured plant-based diet not only provides the necessary nutrients but also can help in the prevention of many diseases.

The burden and risks of emerging complications of diabetes mellitus

The traditional complications of diabetes mellitus are well known and continue to pose a considerable burden on millions of people living with diabetes mellitus. However, advances in the management of diabetes mellitus and, consequently, longer life expectancies, have resulted in the emergence of evidence of the existence of a different set of lesser-acknowledged diabetes mellitus complications. With declining mortality from vascular disease, which once accounted for more than 50% of deaths amongst people with diabetes mellitus, cancer and dementia now comprise the leading causes of death in people with diabetes mellitus in some countries or regions. Additionally, studies have demonstrated notable links between diabetes mellitus and a broad range of comorbidities, including cognitive decline, functional disability, affective disorders, obstructive sleep apnoea and liver disease, and have refined our understanding of the association between diabetes mellitus and infection. However, no published review currently synthesizes this evidence to provide an in-depth discussion of the burden and risks of these emerging complications. This Review summarizes information from systematic reviews and major cohort studies regarding emerging complications of type 1 and type 2 diabetes mellitus to identify and quantify associations, highlight gaps and discrepancies in the evidence, and consider implications for the future management of diabetes mellitus.

Effects of Nutrition Intervention on Blood Glucose, Body Composition, and Phase Angle in Obese and Overweight Patients with Diabetic Foot Ulcers

Nutrition can play an important role in the treatment of chronic wounds such as diabetic foot ulcers (DFUs); however, diet therapy is not currently part of the standard care for DFUs. There are numerous controversies about dietary recommendations, especially regarding calories and macronutrients, for overweight and obese patients with DFUs. This study examined the effects of nutrition education and supplementation on body composition in overweight and obese patients with DFUs. Twenty-nine patients with DFUs between the ages of 30 and 70 years were randomly assigned to either the treatment group (nutritional supplements, diet education, and standard care) or the control group (standard care). At baseline, the mean body mass index (BMI) was 33.5 kg/m2 for the treatment group and 34.1 kg/m2 for the control group. HbA1c decreased in both groups, with no significant difference between the groups. On average, patients in the treatment group lost less lean body mass and gained less fat than the control group ((3.8 kg vs. 4.9 kg) and (0.9 kg vs. 3.6 kg), respectively). While the interaction between group and time did not reach statistical significance for any of the study variables after adjustments for confounding variables, the observed changes are clinically relevant.

Inflammation: Roles in Skeletal Muscle Atrophy

Various diseases can cause skeletal muscle atrophy, usually accompanied by inflammation, mitochondrial dysfunction, apoptosis, decreased protein synthesis, and enhanced proteolysis. The underlying mechanism of inflammation in skeletal muscle atrophy is extremely complex and has not been fully elucidated, thus hindering the development of effective therapeutic drugs and preventive measures for skeletal muscle atrophy. In this review, we elaborate on protein degradation pathways, including the ubiquitin-proteasome system (UPS), the autophagy-lysosome pathway (ALP), the calpain and caspase pathways, the insulin growth factor 1/Akt protein synthesis pathway, myostatin, and muscle satellite cells, in the process of muscle atrophy. Under an inflammatory environment, various pro-inflammatory cytokines directly act on nuclear factor-κB, p38MAPK, and JAK/STAT pathways through the corresponding receptors, and then are involved in muscle atrophy. Inflammation can also indirectly trigger skeletal muscle atrophy by changing the metabolic state of other tissues or cells. This paper explores the changes in the hypothalamic-pituitary-adrenal axis and fat metabolism under inflammatory conditions as well as their effects on skeletal muscle. Moreover, this paper also reviews various signaling pathways related to muscle atrophy under inflammatory conditions, such as cachexia, sepsis, type 2 diabetes mellitus, obesity, chronic obstructive pulmonary disease, chronic kidney disease, and nerve injury. Finally, this paper summarizes anti-amyotrophic drugs and their therapeutic targets for inflammation in recent years. Overall, inflammation is a key factor causing skeletal muscle atrophy, and anti-inflammation might be an effective strategy for the treatment of skeletal muscle atrophy. Various inflammatory factors and their downstream pathways are considered promising targets for the treatment and prevention of skeletal muscle atrophy.

Diabetic sarcopenia: metabolic and molecular appraisal

Myopathy is the missing slot from the routine clinical checkup for diabetic complications. Similarly, its pathophysiological, metabolic, and molecular bases are insufficiently explored. In this review, the above issues are highlighted with a focus on skeletal muscle atrophy (also described as diabetic sarcopenia), in contrast to the normal histological, physiological, and molecular features of the muscles. Literature search using published data from different online resources was used. Several diabetic myopathy etiological factors are discussed explicitly including; inflammation and immunological responses, with emphasis on TNFα and IL-6 overproduction, oxidative stress, neuropathy and vasculopathy, aging sarcopenia, antidiabetic drugs, and insulin resistance as a denominator. The pathophysiological hallmark of diabetic muscle atrophy is the decreased muscle proteins synthesis and increased degradation. The muscle protein degradation is conveyed by 4 systems; ubiquitin-proteasome, lysosomal autophagy, caspase-3, and calpain systems, and is mostly mediated via the IL6/STAT, TNF&IL6/NFκB, myostatin/Smad2/3, and FOXO1/3 signaling pathways, while the protein synthesis inhibition is mediated via suppression of the IGF1-PI3K-Akt-mTOR, and SC-Gαi2-pathways. Moreover, the satellite cells and multilineage muscle mesenchymal progenitor cells differentiation plays a major role on the fate of the affected muscle cells by taking an adipogenic, fibrogenic, or connective tissue lineage. As a conclusion, in this article, the pathological features of diabetic sarcopenia are reviewed at gross level, while at a molecular level the normal protein turnover, signal transduction, and pathways involved in muscle atrophy are described. Finally, an integrated network describing the molecular partakers in diabetic sarcopenia is presented.

A Review of the Potential Consequences of Pearl Millet (Pennisetum glaucum) for Diabetes Mellitus and Other Biomedical Applications

Diabetes mellitus has become a troublesome and increasingly widespread condition. Treatment strategies for diabetes prevention in high-risk as well as in affected individuals are largely attributed to improvements in lifestyle and dietary control. Therefore, it is important to understand the nutritional factors to be used in dietary intervention. A decreased risk of diabetes is associated with daily intake of millet-based foods. Pearl millet is a highly nutritious grain, nutritionally comparable and even superior in calories, protein, vitamins, and minerals to other large cereals, although its intake is confined to lower income segments of society. Pearl millet contains phenolic compounds which possess antidiabetic activity. Thus, it can be used to prepare a variety of food products for diabetes mellitus. Moreover, it also has many health benefits, including combating diabetes mellitus, cancer, cardiovascular conditions, decreasing tumour occurrence, lowering blood pressure, heart disease risk, cholesterol, and fat absorption rate. Therefore, the current review addresses the role of pearl millet in managing diabetes.

Effect of performing high-intensity interval training and resistance training on the same day vs. different days in women with type 2 diabetes

Type 2 diabetes (T2D) is associated with chronic inflammation as a critical factor for muscle atrophy and disease progression. Although the combination of aerobic and resistance training leads to more significant improvements in health-related indices for T2D patients, the interference effect in concurrent training can decrease positive adaptations. The purpose of this study was to investigate the physiological adaptations in performing high-intensity interval training (HIIT) and resistance training on the same day vs. different days in T2D patients. Twenty-four non-athletic 45-65-year-old women with T2D participated in an 8-week intervention. They were randomly divided into three groups: same days (SD), different days (DD), and treatment as usual (control). SD group had resistance training followed by HIIT on Saturday, Monday, and Wednesday. In contrast, the DD group had the same volume of resistance training on Saturday, Monday, and Wednesday and HIIT on Sunday, Tuesday, and Thursday, with Friday as a resting day. Blood samples were collected 24 h before the first and 48 h after the last session in each group to measure glucose, insulin, glycosylated hemoglobin, IGF1, IL1β, CRP, lipid profile, miR-146a, and miR-29b. Three subjects dropped out during the study, and 21 participants (SD = 7, DD = 6, Control = 8) completed the 8-week intervention. MiR-146a changed significantly (P = 0.006) in both SD and DD groups compared to the control group. IGF1 (P = 0.001) and fat-free mass (P = 0.001) changed significantly in SD and DD groups compared to the control group, and also DD led to more significant increases in IGF1 and fat-free mass in comparison with SD. MiR-29 (P = 0.001) changed significantly in the DD group compared to the control group. The reduction of IL-1β, fat mass and insulin resistance was significant in SD and DD compared to the control group; DD showed more potent effects than the SD group on the fat mass (P = 0.001) and insulin resistance (P = 0.001). This study demonstrated that a combination of HIIT and resistance training could be practical for improving health-related outcomes in T2D. Our study indicated for the first time that training strength and HIIT on separate days appeared to be more effective to combat muscle atrophy and insulin resistance.

Skeletal muscle gene expression in older adults with type 2 diabetes mellitus undergoing calorie-restricted diet and recreational sports training - a randomized clinical trial

AIMS

This study aimed to evaluate the impact of a 12-week calorie-restricted diet and recreational sports training on gene expressions IL15, ATROGIN1 and MURF-1 in skeletal muscle of T2D patients.

METHODS

Older adults with T2D (n = 39, 60 ± 6.0 years, BMI 33.5 ± 0.6 kg/m²) were randomly allocated to Diet+Soccer (DS), Diet+Running (DR) or Diet (D). The training sessions were moderate-to-high-intensity and performed 3 × 40 min/week for 12-weeks. Gene expression from vastus lateralis muscle obtained by qRT-PCR, dual-energy X-ray and fasting blood testing measurements were performed before and after 12-weeks. Statistical analysis adopted were two-way ANOVA and Paired t-test for gene expression, and RM-ANOVA test for the remainder variables.

RESULTS

Total body weight was reduced in ~4 kg representing body fat mass in all groups after 12-weeks (P < 0.05). HbA1c values decreased in all groups post-intervention. Lipids profile improved in the training groups (P < 0.05) after 12-weeks. ATROGIN1 and MURF-1 mRNA reduced in the DS (1.084 ± 0.14 vs. 0.754 ± 1.14 and (1.175 ± 0.34 vs. 0.693 ± 0.12, respectively; P < 0.05), while IL15 mRNA increased in the DR (1056 ± 0,12 vs. 1308 ± 0,13; P < 0.05) after 12-weeks intervention.

CONCLUSION

Recreational training with a moderate calorie-restricted diet can downregulates the expression of atrophy-associated myokines and increases the expression of anti-inflammatory gene IL15.

Type 2 Diabetes as a Predictor of Muscle Strength Decline over 11 years among Men and Women Aged 55 Years and Older

BACKGROUND

Long-term associations between type 2 diabetes, prediabetes, and muscle strength are obscure in older adults. The aim of this study was to examine type 2 diabetes as a predictor of handgrip strength decline during an 11-year follow-up among men and women aged 55 years.

METHODS

We used Finnish population-based Health 2000 Survey and its follow-up measurements in 2011. The study population consisted of 1,200 individuals, aged 55-86 years at baseline. Baseline fasting glucose level or use of diabetes medication was used to categorize the participants into diabetes (≥7.0 mmol/L), prediabetes (≥6.1 mmol/L but <7.0 mmol/L), and nondiabetes (<6.1 mmol/L) groups. Handgrip strength was measured at baseline and during 11-year follow-up.

RESULTS

Mean handgrip strength at baseline did not differ between diabetes groups in men or women. Among men during the 11-year follow-up, decline in muscle strength was significantly greater among diabetes group (-131.5 Newtons [N], 95% confidence interval (CI) -182.7 to -80.4) than nondiabetes group (-98.9 N, 95% CI -139.5 to -58.3) after adjusting for age, education, lifestyle factors, chronic conditions, and diabetes status at follow-up. Among women, muscle strength decline did not differ between diabetes, prediabetes, or nondiabetes groups after adjusting for all potential covariates, the results being -45.0 N (95% CI -73.2 to -16.7), -29.4 N (95% CI -59.7 to 0.9), and -42.3 N (95% CI -70.5 to -14.1), respectively.

CONCLUSIONS

The presence of type 2 diabetes was associated with greater muscle strength decline among older men but not among older women.

Protein blend and casein supplementations before inactive phase similarly activate mechanistic target of rapamycin signaling in rat skeletal muscle

During overnight sleep, the longest postabsorptive and inactive phase of the day causes protein catabolism and loss. However, the daytime ingestion of dairy proteins has been shown to stimulate muscle protein synthesis and growth. This study compared the effects of pre-sleep supplementation of a protein blend (PB) composed of micellar casein (MCa) and whey protein (1:1) versus isolate MCa on the plasma levels of branched-chain amino acids (BCAAs) and the activation of the mechanistic target of rapamycin (mTOR) signaling, a critical intracellular pathway involved in the regulation of muscle protein synthesis. After 10 h of fasting during the active phase, rats were fed with a single dose of PB or MCa (5.6 g protein/kg of body mass) by gavage, and samples of blood and gastrocnemius muscle were collected at 30, 90, and 450 min. PB and MCa supplementations induced an increase (~3-fold, P < 0.001) of plasma BCAAs at 30 and 90 min. Most importantly, the stimulatory phosphorylation levels of mTOR and its downstream target p70 ribosomal protein S6 kinase (p70S6K) were similarly higher (~2.5-fold, P < 0.001) 30 and 90 min after MCa and PB. Plasma levels of leucine, isoleucine, valine, and overall BCAAs were correlated with the activation of mTOR (P < 0.001) and p70S6K (P < 0.001). MCa and PB supplementations before the inactive phase of rats resulted in an anabolic milieu in the skeletal muscle by inducing a transient increase in plasma BCAAs and a similar activation of the mTOR/p70S6K axis.

Glucose and protein metabolic responses to an energy- but not protein- restricted diet in type 2 diabetes

AIMS

To test the effect of energy restriction with maintained protein intake on body composition and on insulin sensitivity of glucose and protein metabolism in adults with type 2 diabetes (T2D).

MATERIALS AND METHODS

After 3 days of an isoenergetic diet with 1.2 g/kg/d protein, obese adults with T2D (three women, two men) followed a 5-week diet providing 60% of energy requirements with 45% carbohydrate, and with protein maintained at pre-intervention level. Isotopic tracers were used to quantify whole-body glucose (3-³ H-glucose) and protein (¹³ C-leucine) metabolism pre- (day 4) and post-intervention (day 39), in the postabsorptive state and during a hyperinsulinaemic, isoglycaemic, isoaminoacidaemic clamp. Body composition was measured using dual-energy x-ray absorptiometry.

RESULTS

After energy restriction, 6% weight loss occurred via total body (11%) and visceral fat losses (25%), but lean mass was preserved. Fasting glucose level, serum insulin level, homeostatic model assessment of insulin resistance index and C-peptide level decreased significantly (29%, 38%, 54% and 38%, respectively) as did other cardiometabolic risk factors. Between clamp studies, postabsorptive protein turnover and oxidation rates decreased (12% and 32%), resulting in less negative net balance, consistent with protein conservation. The rates of glucose turnover decreased, and glucose metabolic clearance rate improved (24%). During the clamp, protein flux was lower (9%) and breakdown suppressed (12%), and net balance became less negative but not different. Although glucose turnover did not differ, metabolic clearance improved by 47%.

CONCLUSIONS

In obese adults with T2D, an energy-restricted diet with maintained protein intake of ~1.2 g/kg/d improved the kinetics of protein metabolism (particularly in the postabsorptive state), and preserved lean body mass and increased glucose metabolic clearance rate.

The Relationship between Protein Intake and Source on Factors Associated with Glycemic Control in Individuals with Prediabetes and Type 2 Diabetes

Type 2 diabetes (T2D) is a major contributor to morbidity and mortality largely due to increased cardiovascular disease risk. This study examined the relationships among protein consumption and sources on glycemic control and cardiovascular health in individuals with prediabetes and T2D. Sixty-two overweight or obese participants with prediabetes or T2D, aged 45–75 years were stratified into the following three groups based on protein intake: <0.8 g (gram)/kg (kilogram) body weight (bw), ≥0.8 but <1.0 g/kg bw, and ≥1.0 g/kg bw as below, meeting, and above the recommended levels of protein intake, respectively. Body mass, body mass index (BMI), hip circumference (HC), waist circumference (WC), lean mass, and fat mass (FM) were significantly higher in participants who consumed below the recommended level of protein intake as compared with other groups. Higher animal protein intake was associated with greater insulin secretion and lower triglycerides (TG). Total, low-density, and high-density cholesterol were significantly higher in participants who met the recommended protein intake as compared with the other groups. These data suggest that high protein consumption is associated with lower BMI, HC, WC, and FM, and can improve insulin resistance without affecting lipid profiles in this population. Furthermore, higher intake of animal protein can improve β-cell function and lower plasma TG.

Evaluation of hepatic CYP2D1 activity and hepatic clearance in type I and type II diabetic rat models, before and after treatment with insulin and metformin

INTRODUCTION

Conversion in the metabolism of drugs occurs in diabetes mellitus. Considering the importance of metabolic enzymes' activities on the efficacy and safety of medicines, the changes in liver enzymatic activity of CYP2D1 and its related hepatic clearance, by using Dextromethorphan as probe in the animal model of type I and type II diabetes, before and after treatment, was assessed in this study.

METHODS

Male Wistar rats were randomly divided into 6 groups. Seven days after induction of diabetes type I and type II, treatment groups were received insulin and metformin daily for 14 days, respectively. In day 21, rats were subjected to liver perfusion by Krebs-Henseleit buffer containing Dextromethorphan as CYP2D1 probe. Perfusate samples were analyzed by HPLC fluorescence method in order to evaluate any changes in CYP2D1 activity.

RESULTS

The average metabolic ratio of dextromethorphan and hepatic clearance were changed from 0.012 ± 0.004 and 6.3 ± 0.1 in the control group to 0.006 ± 0.0008 and 5.2 ± 0.2 in the untreated type I diabetic group, and 0.008 ± 0.003 and 5.0 ± 0.6 in the untreated type II diabetic rats. Finally, the mean metabolic ratio and hepatic clearance were changed to 0.008 ± 0.001 and 5.4 ± 0.1, and 0.013 ± 0.003 and 6.1 ± 0.4 in the treated groups with insulin and metformin, respectively.

CONCLUSION

In type I diabetic rats, corresponding treatment could slightly improve enzyme activity, whereas the hepatic clearance and enzyme activity reached to the normal level in type II group. Graphical abstract .

Phytohormones: Multifunctional nutraceuticals against metabolic syndrome and comorbid diseases

Metabolic syndrome is characterized by the co-occurrence of diverse symptoms initiating the development of type 2 diabetes, cardiovascular diseases, and a variety of comorbid diseases. The complex constellation of numerous comorbidities makes it difficult to develop common therapeutic approaches that ameliorate these pathological features simultaneously. The plant hormones abscisic acid, salicylic acid, auxin, and cytokinins, have shown promising anti-inflammatory and pro-metabolic effects that could mitigate several disorders relevant to metabolic syndrome. Intriguingly, besides plants, human cells and gut microbes also endogenously produce these molecules, indicating a role in the complex interplay between inflammatory responses associated with metabolic syndrome, the gut microbiome, and nutrition. Here, we introduce how bioactive phytohormones can be generated endogenously and through the gut microbiome. These molecules subsequently influence immune responses and metabolism. We also elaborate on how phytohormones can beneficially modulate metabolic syndrome comorbidities, and propose them as nutraceuticals.

Exercise and Muscle Atrophy

The incidence of muscle atrophy is increasing with each passing year, which imposes a huge burden on the quality of life of patients. It is a public health issue that causes a growing concern around the world. Exercise is one of the key strategies to prevent and treat various diseases. Appropriate exercise is conducive to compensatory muscle hypertrophy, to improve muscle strength and elasticity, and to train muscle coordination, which is also beneficial to the recovery of skeletal muscle function and the regeneration of muscle cells. Sequelae of paralysis of patients with limb dyskinesia caused by muscle atrophy will be significantly alleviated after regular exercise therapy. Furthermore, exercise therapy can slow down or even reverse muscle atrophy. This article aims to introduce the characteristics of muscle atrophy and summarize the role and mechanism of exercise in the treatment of muscle atrophy in the existing studies, in order to further explore the mechanism of exercise to protect muscle atrophy and provide protection for patients with muscular atrophy.

MILK WHEY PROCESSING: PROSPECTS IN UKRAINE

Milk processing not only makes the production of traditional dairy foods possible, but it is also followed by the formation of by-products, which are not fully utilized, and their emissions into wastewater worsen the environment. The modern technical and technological level of milk processing allows the full use of by-products, which are a source of whey proteins, lactose and other potentially useful ingredients at their base. Amid the decrease in milk production in recent years, an urgent problem is to increase the rank of milk processing in order to obtain products with high added value. The article presents the results of analytical studies of the state of the issue of whey processing in Ukraine. Modern conceptual approaches to solve the problems of processing various types of whey, which is formed as a by-product in the production of cheeses, cottage cheese, casein, are presented. The new types of products and ingredients obtained from whey, having a wide range of functional and technological properties and being in demand in the production of food products, are shown. The development trends of the novelty technologies for obtaining a wide range of whey-based products and ingredients are analyzed, new research data on their role in ensuring human health are presented. The review article reviews and justifies the feasibility of introducing modern membrane technologies for whey processing at domestic milk processing enterprises, this allowing rational use of raw milk resources, reducing negative environmental impact, and increasing production profitability. The results of scientific and applied research using membrane methods and enzymatic hydrolysis of lactose in technologies of dry demineralized whey and condensed low-lactose whey, are presented. The use of existing industrial equipment allows, due to changes in the protein-mineral composition of whey, obtaining products with a wide range of functional and technological properties and increased nutritional values.

Dietary protein and exercise for preservation of lean mass and perspectives on type 2 diabetes prevention

Sedentary lifestyle and aging favor the increasing prevalence of obesity and type 2 diabetes and their comorbidities. The loss of lean body mass reduces muscle strength, resulting in impaired functional capacity and leading to increased risks of chronic diseases with advancing age. Besides aging, conditions such as inappetence, social isolation, and inadequate dietary intake cause the loss of lean body mass and increased abdominal fatty mass, resulting in sarcopenic obesity and predisposition to type 2 diabetes. Compared to younger people, this condition is more common in the elderly owing to natural changes in body composition associated with aging. Lifestyle changes such as increased physical activity and improved dietary behaviors are effective for preventing the occurrence of comorbidities. Regarding muscle nutrition, besides caloric adequacy, meeting the requirements for the consumption of dietary amino acids and proteins is important for treating sarcopenia and sarcopenic obesity because muscle tissue mainly consists of proteins and is, therefore, the largest reservoir of amino acids in the body. Thus, this review discusses the effects of dietary protein on the preservation of lean body mass, improvements in the functional capacity of muscle tissue, and prevention of chronic diseases such as type 2 diabetes. In addition, we address the effects of regular physical training associated with dietary protein strategies on lean body mass, body fat loss, and muscle strength in the elderly at a risk for type 2 diabetes development.

Type 2 diabetes causes skeletal muscle atrophy but does not impair resistance training-mediated myonuclear accretion and muscle mass gain in rats

New Findings

What is the central question of this study?

Type 2 diabetes mellitus (T2DM) causes skeletal muscle atrophy; does it affect resistance training (RT)‐mediated molecular adaptations and subsequent muscle hypertrophy?

What is the main finding and its importance?

Although skeletal muscle mass and regulation were not preserved under conditions of T2DM, the response of RT‐induced skeletal muscle hypertrophy was not impaired in T2DM rat skeletal muscle. These findings suggest that the capacity of RT‐mediated muscle mass gain is not diminished in the T2DM condition.

Abstract

Type 2 diabetes mellitus (T2DM) is known to cause skeletal muscle atrophy. However, it is not known whether T2DM affects resistance training (RT)‐mediated molecular adaptations and subsequent muscle hypertrophy. Therefore, we investigated the effect of T2DM on response of skeletal muscle hypertrophy to chronic RT using a rat resistance exercise mimetic model. T2DM and healthy control rats were subjected to 18 bouts (3 times per week) of chronic RT on unilateral lower legs. RT significantly increased gastrocnemius muscle mass and myonuclei in both T2DM and healthy control rats to the same extent, even though T2DM caused muscle atrophy in the resting condition. Further, T2DM significantly reduced mechanistic target of rapamycin complex 1 (mTORC1) activity (phosphorylation of p70S6K^Thr389 and 4E‐BP1^Thr37/46) to insulin stimulation and the number of myonuclei in the untrained basal condition, but RT‐mediated adaptations were not affected by T2DM. These findings suggested that although the skeletal muscle mass and regulation were not preserved under basal conditions of T2DM, the response of RT‐induced skeletal muscle hypertrophy was not impaired in T2DM rat skeletal muscle.

Myostatin alters with exercise training in diabetic rats; possible interaction with glycosylated hemoglobin and inflammatory cytokines

The role of myostatin (MSTN) in the regulation of energy homeostasis has been known and that MSTN inhibition can attenuate the development of diabetes. However, the response of MSTN to exercise in type 1 diabetes (T1DM) is unknown. This study aimed to investigate the alteration of MSTN following aerobic exercise training in diabetic rats and its possible interaction with glycosylated hemoglobin (HbA1c) and inflammatory cytokines. Forty-eight male Wistar rats were divided into non-diabetic untrained, non-diabetic trained, diabetic untrained and diabetic trained groups. To induce T1DM, rats received an intraperitoneal injection of STZ (60 mg·kg^-1). Treadmill exercise was performed for six weeks, five days/week. HbA1c was estimated, MSTN mRNA expression in skeletal muscle was measured, and plasma MSTN and inflammatory cytokines including interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) were determined. Results revealed a significant decrease of HbA1c and plasma inflammatory cytokines (IL-6, TNF-α and IL-1β) followed by a significant decrease of plasma and skeletal muscle MSTN in diabetic trained rats versus non-diabetic untrained and diabetic untrained rats after the experimental period. Moreover, in diabetic untrained and diabetic trained rats, a significantly positive correlation (change versus change) of plasma MSTN with HbA1c and plasma IL-6, TNF-α and IL-1β was found. In conclusion, this study indicated that aerobic exercise training by a decrease of HbA1c and plasma IL-6, TNF-α and IL-1β could decrease MSTN levels in plasma and skeletal muscle in T1DM. Furthermore, the effective influence of exercise may be reflected by changes of MSTN in diabetic rats.

The Relationship Between Sleep Duration, Falls, and Muscle Mass: A Cohort Study in an Elderly Chinese Population

Epidemiological studies report that more than half of the people over the age of 65 years suffer from variable sleep problems. In this study, we conducted a cohort study to investigate the relationship between sleep duration, muscle mass, and function within a community-dwelling, elderly Chinese population. Our study population consisted of residents living in the township central hospital of suburban Tianjin, China. We measured muscle strength and walking speed. We divided sleep duration into the following four groups: <7 hours, 7-8 hours, >8-9 hours, and >9 hours. A total of 902 participants completed the 3-year follow-up. We observed a U-shaped relationship between sleep duration and fall risk. Compared with the 7-8-hour group, fall risk within the <7-hour group was 3.67 (2.59, 5.42) times higher and fall risk within the >9-hour group was 2.35 (1.29, 3.52) times higher. After adjustment, muscle mass declined by -6.82% (-11.27%, -3.83%) in the <7-hour group. In summary, we observed a U-shaped relationship between sleep duration and falls. Short sleep duration has a negative relationship with muscle mass decline in a community-dwelling, elderly Chinese population.

PPARγ Controls Ectopic Adipogenesis and Cross-Talks with Myogenesis During Skeletal Muscle Regeneration

Skeletal muscle is a regenerative tissue which can repair damaged myofibers through the activation of tissue-resident muscle stem cells (MuSCs). Many muscle diseases with impaired regeneration cause excessive adipose tissue accumulation in muscle, alter the myogenic fate of MuSCs, and deregulate the cross-talk between MuSCs and fibro/adipogenic progenitors (FAPs), a bi-potent cell population which supports myogenesis and controls intra-muscular fibrosis and adipocyte formation. In order to better characterize the interaction between adipogenesis and myogenesis, we studied muscle regeneration and MuSC function in whole body Pparg null mice generated by epiblast-specific Cre/lox deletion (Pparg^Δ/Δ). We demonstrate that deletion of PPARγ completely abolishes ectopic muscle adipogenesis during regeneration and impairs MuSC expansion and myogenesis after injury. Ex vivo assays revealed that perturbed myogenesis in Pparg^Δ/Δ mice does not primarily result from intrinsic defects of MuSCs or from perturbed myogenic support from FAPs. The immune transition from a pro- to anti-inflammatory MuSC niche during regeneration is perturbed in Pparg^Δ/Δ mice and suggests that PPARγ signaling in macrophages can interact with ectopic adipogenesis and influence muscle regeneration. Altogether, our study demonstrates that a PPARγ-dependent adipogenic response regulates muscle fat infiltration during regeneration and that PPARγ is required for MuSC function and efficient muscle repair.

Poor toe flexor strength, but not handgrip strength, is associated with the prevalence of diabetes mellitus in middle-aged males

Previous studies suggested that reduced muscular strength was one of the potential predictor of prevalence of diabetes mellitus. The purpose of this study was to investigate the association between toe flexor strength (TFS) and handgrip strength (HGS) and the prevalence of diabetes mellitus. Cross-sectional analysis was conducted using data from 1,390 Japanese males (35-59 years). TFS and HGS were measured and medical examinations undertaken. The prevalence of diabetes mellitus was defined as fasting blood glucose ≥126 mg/dL, glycated hemoglobin ≥6.5% (48 mmol/mol), and/or current use of anti-diabetes mellitus drugs. A total of 114 participants had diabetes mellitus. TFS in participants with diabetes mellitus was significantly lower than that in persons not suffering from diabetes mellitus but HGS was not. Odds ratio (OR) and 95% confidence interval (CI) per 1-standard deviation-increase in muscular strength measurements for the prevalence of diabetes mellitus were obtained using a multiple logistic regression model. Prevalence of diabetes mellitus was inversely related to TFS (OR 0.769, 95% CI 0.614-0.963), TFS/body mass (BM) (0.696, 0.545-0.889) and TFS/body mass index (BMI) (0.690, 0.539-0.882) after adjustment of covariates. Such associations were not observed in HGS (OR 0.976, 95% CI 0.773-1.232), HGS/BM (0.868, 0.666-1.133) or HGS/BMI (0.826, 0.642-1.062). These results suggested that poor TFS was associated with an increased prevalence of diabetes mellitus independent of visceral fat accumulation, but HGS was not, in middle-aged males. TFS may be a better marker for the prevalence of diabetes mellitus than HGS.

Sleep, Muscle Mass and Muscle Function in Older People

BACKGROUND

Loss of muscle mass, particularly in old age, can restrict mobility and physical function. Sleep is thought to play a key role in the maintenance of muscle mass; sleep disturbances have a prevalence of 6-30% in Germany. In this study, based on data from the Berlin Aging Study II (BASE-II), we analyze the relationship between sleep efficiency and quality on the one hand, and muscle mass and muscle function on the other.

METHODS

We analyzed cross-sectional data from 1196 subjects (52.5% women; 68 ± 4 years). Sleep behavior was assessed with questions from the Pittsburgh Sleep Quality Index; appendicular lean mass (ALM) with dual x-ray absorp - tiometry; and muscle function with a measure of grip strength and with questionnaires about physical activity and impairment of physical activities. Low muscle mass was determined from the ALM corrected by the body-mass index (BMI), i.e., from the ratio ALM/BMI.

RESULTS

19.1% of the women and 13.4% of the men reported poor sleep quality. Men whose ALM/BMI ratio was below the cutoff value for low muscle mass more frequently reported very poor sleep efficiency (9.1% , versus 4.8% in women; p<0.002). The adjusted odds ratio for low muscle mass was 2.8 for men with poor sleep quality (95% confidence interval: [1.1; 6.7]) and 4.3 for men with poor sleep efficiency [1.2; 15.1]. In women, there was no statistically significant association between sleep quality and efficiency on the one hand and ALM/BMI values below cutoff on the other, but poor sleep quality was found to be associated with reduced grip strength (16.25 kg ± 2.33 kg versus 15.67 kg ± 2.38 kg; p = 0.009) and low appendicular lean mass (ALM: 16.25 kg ± 2.33 kg versus 15.67 kg ± 2.38 kg; p = 0.016).

CONCLUSION

These findings support the hypothesis of a link between sleep and muscle mass. The dependence of muscle mass on sleep behavior needs to be investigated in longitudinal studies.

Sarcopenia in elderly patients with type 2 diabetes mellitus: prevalence and related clinical factors

Aims

Sarcopenia, which shortens healthy life expectancy, has recently been attracting attention because the Japanese population is rapidly aging. In this preliminary study, we estimated the prevalence of elderly diabetic patients who were complicated with sarcopenia and searched for any related clinical factors.

Methods

Elderly (≥65 years of age) Japanese patients with type 2 diabetes mellitus were recruited by asking doctors to supply candidates for the study. The prevalence of sarcopenia was estimated based on the criteria proposed by the Asian Working Group for Sarcopenia in 2014.

Results

Two hundred eighty-eight patients (151 males) were accepted for the study. The prevalence of sarcopenia was 15.2% in males and 15.3% in females. Multiple logistic regression analysis indicated that sarcopenia was significantly correlated with serum high-sensitivity C-reactive protein in females, in addition to age and body mass index. Female patients were then classified into four groups according to the presence or absence of impaired muscle mass and/or impaired strength. Serum high-sensitivity C-reactive protein was significantly higher in the sarcopenia group (those with impaired muscle mass and impaired strength) than in the other three groups.

Conclusions

After clarifying the prevalence of sarcopenia in elderly Japanese patients with type 2 diabetes mellitus, we found that serum high-sensitivity C-reactive protein was significantly higher in female patients with sarcopenia than in female patients without sarcopenia. Elevated serum high-sensitivity C-reactive protein requires impaired muscle mass and impaired strength.

Exercise, oxidants, and antioxidants change the shape of the bell-shaped hormesis curve

It is debated whether exercise-induced ROS production is obligatory to cause adaptive response. It is also claimed that antioxidant treatment could eliminate the adaptive response, which appears to be systemic and reportedly reduces the incidence of a wide range of diseases. Here we suggest that if the antioxidant treatment occurs before the physiological function-ROS dose-response curve reaches peak level, the antioxidants can attenuate function. On the other hand, if the antioxidant treatment takes place after the summit of the bell-shaped dose response curve, antioxidant treatment would have beneficial effects on function. We suggest that the effects of antioxidant treatment are dependent on the intensity of exercise, since the adaptive response, which is multi pathway dependent, is strongly influenced by exercise intensity. It is further suggested that levels of ROS concentration are associated with peak physiological function and can be extended by physical fitness level and this could be the basis for exercise pre-conditioning. Physical inactivity, aging or pathological disorders increase the sensitivity to oxidative stress by altering the bell-shaped dose response curve.

Dysregulation between TRIM63/FBXO32 expression and soleus muscle wasting in diabetic rats: potential role of miR-1-3p, -29a/b-3p, and -133a/b-3p

Diabetes mellitus (DM) induces a variable degree of muscle sarcopenia, which may be related to protein degradation and to the expression of both E3 ubiquitin ligases and some specific microRNAs (miRNAs). The present study investigated the effect of diabetes and acute muscle contraction upon the TRIM63 and FBXO32 expression as well as the potential involvement of some miRNAs. Diabetes was induced by streptozotocin and studied after 30 days. Soleus muscles were harvested, stimulated to contract in vitro for twitch tension analysis (0.5 Hz), 30 min later for tetanic analysis (100 Hz), and 30 min later were frozen. TRIM63 and FBXO32 proteins were quantified by western blotting; Trim63 mRNA, Fbxo32 mRNA, miR-1-3p, miR-29a-3p, miR-29b-3p, miR-133a-3p, and miR-133b-3p were quantified by qPCR. Diabetes induced sarcopenia by decreasing (P < 0.05) muscle weight/tibia length index, maximum tetanic contraction and relaxation rates, and absolute twitch and tetanic forces (P < 0.05). Diabetes decreased (P < 0.05) the Trim63 and Fbxo32 mRNAs (30%) and respective proteins (60%), and increased (P < 0.01) the miR-29b-3p (2.5-fold). In muscle from diabetic rats, acute contractile stimulus increased TRIM63 protein, miR-1-3p, miR-29a-3p, and miR-133a/b-3p, but decreased miR-29b-3p (P < 0.05). Independent of the metabolic condition, after muscle contraction, both TRIM63 and FBXO32 proteins correlated significantly with miR-1-3p, miR-29a/b-3p, and miR-133a/b-3p. All diabetes-induced regulations were reversed by insulin treatment. Concluding, the results depict that muscle wasting in long-term insulinopenic condition may not be accompanied by increased proteolysis, pointing out the protein synthesis as an important modulator of muscle sarcopenia in DM.

Leucine and Mammalian Target of Rapamycin-Dependent Activation of Muscle Protein Synthesis in Aging

The preservation or restoration of muscle mass is of prime importance for healthy aging. However, aging has been repeatedly shown to be associated with resistance of muscle to the anabolic effects of feeding. Leucine supplementation has been proposed as a possible strategy because of its regulatory role on protein homeostasis. Indeed, it acts independently of growth factors and leads to enhanced cap-dependent mRNA translation initiation and increased protein synthesis. Leucine acts as a signaling molecule directly at the muscle level via the activation of mammalian/mechanistic target of rapamycin complex 1 (mTORC1). However, in aged muscle, mTORC1 activation seems to be impaired, with decreased sensitivity and responsiveness of muscle protein synthesis to amino acids, whereas the phosphorylation state of several components of this signaling pathway appears to be higher in the basal state. This may stem from specific age-related impairment of muscle signaling and from decreased nutrient and growth factor delivery to the muscle. Whether aging per se affects mTORC1 signaling remains to be established, because aging is frequently associated with inadequate protein intake, decreased insulin sensitivity, inactivity, inflammatory processes, etc. Whatever its origin, this anabolic resistance to feeding can be mitigated by quantitative and qualitative manipulation of protein supply, such as leucine supplementation; however, there remains the question of possible adverse effects of long-term, high-dose leucine supplementation in terms of insulin resistance and tumorigenesis.

Dietary Interventions for Type 2 Diabetes: How Millet Comes to Help

Diabetes has become a highly problematic and increasingly prevalent disease world-wide. It has contributed toward 1.5 million deaths in 2012. Management techniques for diabetes prevention in high-risk as well as in affected individuals, beside medication, are mainly through changes in lifestyle and dietary regulation. Particularly, diet can have a great influence on life quality for those that suffer from, as well as those at risk of, diabetes. As such, considerations on nutritional aspects are required to be made to include in dietary intervention. This review aims to give an overview on the general consensus of current dietary and nutritional recommendation for diabetics. In light of such recommendation, the use of plant breeding, conventional as well as more recently developed molecular marker-based breeding and biofortification, are discussed in designing crops with desired characteristics. While there are various recommendations available, dietary choices are restricted by availability due to geo-, political-, or economical- considerations. This particularly holds true for countries such as India, where 65 million people (up from 50 million in 2010) are currently diabetic and their numbers are rising at an alarming rate. Millets are one of the most abundant crops grown in India as well as in Africa, providing a staple food source for many poorest of the poor communities in these countries. The potentials of millets as a dietary component to combat the increasing prevalence of global diabetes are highlighted in this review.

Protein Intake and Muscle Health in Old Age: From Biological Plausibility to Clinical Evidence

The provision of sufficient amounts of dietary proteins is central to muscle health as it ensures the supply of essential amino acids and stimulates protein synthesis. Older persons, in particular, are at high risk of insufficient protein ingestion. Furthermore, the current recommended dietary allowance for protein (0.8 g/kg/day) might be inadequate for maintaining muscle health in older adults, probably as a consequence of "anabolic resistance" in aged muscle. Older individuals therefore need to ingest a greater quantity of protein to maintain muscle function. The quality of protein ingested is also essential to promoting muscle health. Given the role of leucine as the master dietary regulator of muscle protein turnover, the ingestion of protein sources enriched with this essential amino acid, or its metabolite β-hydroxy β-methylbutyrate, is thought to offer the greatest benefit in terms of preservation of muscle mass and function in old age.

Differential control of muscle mass in type 1 and type 2 diabetes mellitus

Diabetes mellitus--whether driven by insulin deficiency or insulin resistance--causes major alterations in muscle metabolism. These alterations have an impact on nutrient handling, including the metabolism of glucose, lipids, and amino acids, and also on muscle mass and strength. However, the ways in which the distinct forms of diabetes affect muscle mass differ greatly. The most common forms of diabetes mellitus are type 1 and type 2. Thus, whereas type 1 diabetic subjects without insulin treatment display a dramatic loss of muscle, most type 2 diabetic subjects show no changes or even an increase in muscle mass. However, the most commonly used rodent models of type 2 diabetes are characterized by muscle atrophy and do not mimic the features of the disease in humans in terms of muscle mass. In this review, we analyze the processes that are differentially regulated under these forms of diabetes and propose regulatory mechanisms to explain them.

Protein Requirements and Recommendations for Older People: A Review

Declines in skeletal muscle mass and strength are major contributors to increased mortality, morbidity and reduced quality of life in older people. Recommended Dietary Allowances/Intakes have failed to adequately consider the protein requirements of the elderly with respect to function. The aim of this paper was to review definitions of optimal protein status and the evidence base for optimal dietary protein. Current recommended protein intakes for older people do not account for the compensatory loss of muscle mass that occurs on lower protein intakes. Older people have lower rates of protein synthesis and whole-body proteolysis in response to an anabolic stimulus (food or resistance exercise). Recommendations for the level of adequate dietary intake of protein for older people should be informed by evidence derived from functional outcomes. Randomized controlled trials report a clear benefit of increased dietary protein on lean mass gain and leg strength, particularly when combined with resistance exercise. There is good consistent evidence (level III-2 to IV) that consumption of 1.0 to 1.3 g/kg/day dietary protein combined with twice-weekly progressive resistance exercise reduces age-related muscle mass loss. Older people appear to require 1.0 to 1.3 g/kg/day dietary protein to optimize physical function, particularly whilst undertaking resistance exercise recommendations.

Combining nutrition and exercise to optimize survival and recovery from critical illness: Conceptual and methodological issues

Survivors of critical illness commonly experience neuromuscular abnormalities, including muscle weakness known as ICU-acquired weakness (ICU-AW). ICU-AW is associated with delayed weaning from mechanical ventilation, extended ICU and hospital stays, more healthcare-related hospital costs, a higher risk of death, and impaired physical functioning and quality of life in the months after ICU admission. These observations speak to the importance of developing new strategies to aid in the physical recovery of acute respiratory failure patients. We posit that to maintain optimal muscle mass, strength and physical function, the combination of nutrition and exercise may have the greatest impact on physical recovery of survivors of critical illness. Randomized trials testing this and related hypotheses are needed. We discussed key methodological issues and proposed a common evaluation framework to stimulate work in this area and standardize our approach to outcome assessments across future studies.

Magnitude of muscle wasting early after on-pump coronary artery bypass graft surgery and exploration of aetiology

NEW FINDINGS

What is the central question of this study? It remains uncertain whether significant fat-free mass wasting occurs early after coronary artery bypass graft surgery, and the aetiology of this wasting in these particular conditions is unexplored. What is the main finding and its importance? Significant fat-free mass wasting is present after coronary artery bypass graft surgery, and this wasting effect is greater in younger patients and in patients with greater increments in blood cortisol-to-testosterone ratios after surgery. The magnitude and aetiology of muscle wasting early after coronary artery bypass graft (CABG) surgery remains unknown. In the present study, we assessed changes in fat-free mass early after CABG surgery and explored the possible aetiology (relationships with postsurgical changes in blood hormones, insulin resistance, subject characteristics and inflammation) for these changes. Fat-free mass was assessed before and 23 (range: 25) days after CABG surgery in 25 subjects. Blood testosterone, cortisol, insulin-like growth factor-1, growth hormone, sex hormone-binding globulin, glucose, insulin, C-peptide and C-reactive protein concentrations were determined, and free androgen index, cortisol-to-testosterone ratio and HOMA-IR index were all calculated before surgery, during the first 3 days after surgery and at reassessment of body composition. Relationships between changes in fat-free mass and changes in blood parameters after surgery or subject characteristics were studied. After surgery, free androgen index and blood sex hormone-binding globulin, testosterone and insulin-like growth factor-1 concentrations decreased significantly, while HOMA-IR index, cortisol-to-testosterone ratio, blood growth hormone, insulin and C-reactive protein concentrations increased significantly (P < 0.0025, observed α > 0.80). Whole-body fat-free mass decreased significantly [by -1.9 (range: 9.1) kg, P < 0.0025, observed α = 0.99] after surgery. According to regression analysis, greater absolute loss of fat-free mass was observed after CABG surgery in subjects who were younger, who experienced a greater increase in blood cortisol-to-testosterone ratio after surgery and/or who underwent earlier reassessment of body composition (P < 0.05). Significant decrements in fat-free mass were observed early after CABG surgery, especially in younger subjects and/or subjects with elevated blood cortisol-to-testosterone ratios after surgery. Interventions to preserve fat-free mass soon after CABG surgery are thus warranted.

Urocortin 3 activates AMPK and AKT pathways and enhances glucose disposal in rat skeletal muscle

Insulin resistance (IR) in skeletal muscle is an important component of both type 2 diabetes and the syndrome of sarcopaenic obesity, for which there are no effective therapies. Urocortins (UCNs) are not only well established as neuropeptides but also have their roles in metabolism in peripheral tissues. We have shown recently that global overexpression of UCN3 resulted in muscular hypertrophy and resistance to the adverse metabolic effects of a high-fat diet. Herein, we aimed to establish whether short-term local UCN3 expression could enhance glucose disposal and insulin signalling in skeletal muscle. UCN3 was found to be expressed in right tibialis cranialis and extensor digitorum longus muscles of rats by in vivo electrotransfer and the effects studied vs the contralateral muscles after 1 week. No increase in muscle mass was detected, but test muscles showed 19% larger muscle fibre diameter (P=0.030), associated with increased IGF1 and IGF1 receptor mRNA and increased SER256 phosphorylation of forkhead transcription factor. Glucose clearance into the test muscles after an intraperitoneal glucose load was increased by 23% (P=0.018) per unit mass, associated with increased GLUT1 (34% increase; P=0.026) and GLUT4 (48% increase; P=0.0009) proteins, and significantly increased phosphorylation of insulin receptor substrate-1, AKT, AKT substrate of 160 kDa, glycogen synthase kinase-3β, AMP-activated protein kinase and its substrate acetyl coA carboxylase. Thus, UCN3 expression enhances glucose disposal and signalling in muscle by an autocrine/paracrine mechanism that is separate from its pro-hypertrophic effects, implying that such a manipulation may have promised for the treatment of IR syndromes including sarcopaenic obesity.

Reversal of muscle atrophy by Zhimu-Huangbai herb-pair via Akt/mTOR/FoxO3 signal pathway in streptozotocin-induced diabetic mice

Skeletal muscle atrophy is one of the serious complications of diabetes. Zhimu-Huangbai herb-pair (ZB) is widely used in Chinese traditional medicine formulas for treating Xiaoke (known as diabetes) and its complications. However, the effect of ZB on reversal of muscle atrophy and the underlying mechanisms remain unknown. In this research, we investigated the effect and possible mechanisms of ZB on skeletal muscle atrophy in diabetic mice. Animal model of diabetic muscle atrophy was developed by high fat diet (HFD) feeding plus streptozotocin (STZ) injection. After oral adminstration of ZB for 6 weeks, the effects of ZB on reversal of muscle atrophy and the underlying mechanisms were evaluated by biochemical, histological and western blot methods. The skeletal muscle weight, strength, and cross-sectional area of diabetic mice were significantly increased by ZB treatment. Biochemical results showed that ZB treatment reduced the serum glucose level, and elevated the serum insulin-like growth factor 1 (IGF-1) and insulin levels significantly compared with untreated diabetic group. The western blot results showed that ZB activated the mTOR signal pathway, shown as increased phosphorylations (p-) of Akt, mTOR, Raptor, S6K1 and reduced Foxo3 expression compared with the model group. ZB could reverse muscle atrophy in diabetic mice. This may be through activation of mTOR signaling pathway that promotes protein synthesis, and inactivation foxo3 protein that inhibits protein degradation. These findings suggested that ZB may be considered as a potential candidate drug in treatment of diabetic muscle atrophy.

Increasing muscle mass improves vascular function in obese (db/db) mice

Background

A sedentary lifestyle is an independent risk factor for cardiovascular disease and exercise has been shown to ameliorate this risk. Inactivity is associated with a loss of muscle mass, which is also reversed with isometric exercise training. The relationship between muscle mass and vascular function is poorly defined. The aims of the current study were to determine whether increasing muscle mass by genetic deletion of myostatin, a negative regulator of muscle growth, can influence vascular function in mesenteric arteries from obese db/db mice.

Methods and Results

Myostatin expression was elevated in skeletal muscle of obese mice and associated with reduced muscle mass (30% to 50%). Myostatin deletion increased muscle mass in lean (40% to 60%) and obese (80% to 115%) mice through increased muscle fiber size (P<0.05). Myostatin deletion decreased adipose tissue in lean mice, but not obese mice. Markers of insulin resistance and glucose tolerance were improved in obese myostatin knockout mice. Obese mice demonstrated an impaired endothelial vasodilation, compared to lean mice. This impairment was improved by superoxide dismutase mimic Tempol. Deletion of myostatin improved endothelial vasodilation in mesenteric arteries in obese, but not in lean, mice. This improvement was blunted by nitric oxide (NO) synthase inhibitor l‐NG‐nitroarginine methyl ester (l‐NAME). Prostacyclin (PGI₂)‐ and endothelium‐derived hyperpolarizing factor (EDHF)‐mediated vasodilation were preserved in obese mice and unaffected by myostatin deletion. Reactive oxygen species) was elevated in the mesenteric endothelium of obese mice and down‐regulated by deletion of myostatin in obese mice. Impaired vasodilation in obese mice was improved by NADPH oxidase inhibitor (GKT136901). Treatment with sepiapterin, which increases levels of tetrahydrobiopterin, improved vasodilation in obese mice, an improvement blocked by l‐NAME.

Conclusions

Increasing muscle mass by genetic deletion of myostatin improves NO‐, but not PGI₂‐ or EDHF‐mediated vasodilation in obese mice; this vasodilation improvement is mediated by down‐regulation of superoxide.

Plasma gelsolin levels decrease in diabetic state and increase upon treatment with F-actin depolymerizing versions of gelsolin

The study aims to map plasma gelsolin (pGSN) levels in diabetic humans and mice models of type II diabetes and to evaluate the efficacy of gelsolin therapy in improvement of diabetes in mice. We report that pGSN values decrease by a factor of 0.45 to 0.5 in the blood of type II diabetic humans and mice models. Oral glucose tolerance test in mice models showed that subcutaneous administration of recombinant pGSN and its F-actin depolymerizing competent versions brought down blood sugar levels comparable to Sitagliptin, a drug used to manage hyperglycemic condition. Further, daily dose of pGSN or its truncated versions to diabetic mice for a week kept sugar levels close to normal values. Also, diabetic mice treated with Sitagliptin for 7 days, showed increase in their pGSN values with the decrease in blood glucose as compared to their levels at the start of treatment. Gelsolin helped in improving glycemic control in diabetic mice. We propose that gelsolin level monitoring and replacement of F-actin severing capable gelsolin(s) should be considered in diabetic care.

Cancer cachexia and diabetes: similarities in metabolic alterations and possible treatment

Cancer cachexia is a metabolic syndrome featuring many alterations typical of type 2 diabetes (T2D). While muscle wasting is a hallmark of cachexia, epidemiological evidence also supports an accelerated age-related muscle loss in T2D. Insulin resistance manifests in both conditions and impairs glucose disposal and protein anabolism by tissues. A greater contribution of gluconeogenesis to glucose production may limit amino acid availability for muscle protein synthesis, further aggravating muscle loss. In the context of inter-dependence between glucose and protein metabolism, the present review summarizes the current state of knowledge on alterations that may lead to muscle wasting in human cancer. By highlighting the similarities with T2D, a disease that has been more extensively studied, the objective of this review is to provide a better understanding of the pathophysiology of cancer cachexia and to consider potential treatments usually targeted for T2D. Nutritional approaches aimed at stimulating protein anabolism might include specially formulated food with optimal protein and amino acid composition. Because the gradual muscle loss in T2D may be attenuated by diabetes treatment, anti-diabetic drugs might be considered in cachexia treatment. Metformin emerges as a choice candidate as it acts both on reducing gluconeogenesis and improving insulin sensitivity, and has demonstrated tumour suppressor properties in multiple cancer types. Such a multimodal approach to slow or reverse muscle wasting in cachexia warrants further investigation.