Effect of GLP-1 receptor agonist, liraglutide, on muscle in spontaneously diabetic torii fatty rats

Liraglutide promotes UCP1 expression and lipolysis of adipocytes by promoting the secretion of irisin from skeletal muscle cells

Although Liraglutide (Lira) increases serum irisin levels in type 2 diabetes mellitus (T2DM), it is unclear whether it induces expression of uncoupling protein 1 (UCP1) of adipocytes via promoting irisin secretion from skeletal muscle. Male T2DM rats were treated with 0.4 mg/kg/d Lira twice a day for 8 weeks, and the protein expression of phosphorylated AMP kinase (p-AMPK), phosphorylated acetyl-CoA carboxylase 1 (p-ACC1) and UCP1 in white adipose tissues were detected. Differentiated C2C12 cells were treated with palmitic acid (PA) and Lira to detect the secretion of irisin. Differentiated 3T3-L1 cells were treated with irisin, supernatant from Lira-treated C2C12 cells, Compound C or siAMPKα1, the triglyceride (TG) content and the related gene expression were measured. The transcriptome in irisin-treated differentiated 3T3-L1 cells was analyzed. Lira elevated serum irisin levels, decreased the adipocyte size and increased the protein expression of UCP1, p-AMPK and p-ACC1 in WAT. Moreover, it promoted the expression of PGC1α and FNDC5, the secretion of irisin in PA-treated differentiated C2C12 cells. The irisin and supernatant decreased TG synthesis and promoted the expression of browning- and lipolysis-related genes in differentiated 3T3-L1 cells. While Compound C and siAMPKα1 blocked AMPK activities and expression, irisin partly reversed the pathway. Finally, the transcriptome analysis indicated that differently expressed genes are mainly involved in browning and lipid metabolism. Overall, our findings showed that Lira modulated muscle-to-adipose signaling pathways in diabetes via irisin-mediated AMPKα/ACC1/UCP1/PPARα pathway. Our results suggest a new mechanism for the treatment of T2DM by Lira.

Correlation of diabetic renal hypoperfusion with microvascular responses of the skeletal muscle: a rat model study using diffuse correlation spectroscopy

Using diffuse correlation spectroscopy, we assessed the renal blood flow and thigh muscle microvascular responses in a rat model of type 2 diabetes. The blood flow index at the renal surface decreased significantly with arterial clamping, cardiac extirpation, and the progression of diabetic endothelial dysfunction. Renal blood flow measured in diabetic and nondiabetic rats also showed a significant correlation with the reactive hyperemic response of the thigh muscle. These results suggest shared microcirculatory dysfunction in the kidney and skeletal muscle and support endothelial responses in the skeletal muscle as a potential noninvasive biomarker of renal hypoperfusion.

Sarcopenia and Diabetes: A Detrimental Liaison of Advancing Age

Sarcopenia is an age-related clinical complaint characterized by the progressive deterioration of skeletal muscle mass and strength over time. Type 2 diabetes (T2D) is associated with faster and more relevant skeletal muscle impairment. Both conditions influence each other, leading to negative consequences on glycemic control, cardiovascular risk, general health status, risk of falls, frailty, overall quality of life, and mortality. PubMed/Medline, Scopus, Web of Science, and Google Scholar were searched for research articles, scientific reports, observational studies, clinical trials, narrative and systematic reviews, and meta-analyses to review the evidence on the pathophysiology of di-abetes-induced sarcopenia, its relevance in terms of glucose control and diabetes-related outcomes, and diagnostic and therapeutic challenges. The review comprehensively addresses key elements for the clinical definition and diagnostic criteria of sarcopenia, the pathophysiological correlation be-tween T2D, sarcopenia, and related outcomes, a critical review of the role of antihyperglycemic treatment on skeletal muscle health, and perspectives on the role of specific treatment targeting myokine signaling pathways involved in glucose control and the regulation of skeletal muscle metabolism and trophism. Prompt diagnosis and adequate management, including lifestyle inter-vention, health diet programs, micronutrient supplementation, physical exercise, and pharmaco-logical treatment, are needed to prevent or delay skeletal muscle deterioration in T2D.

Glucagon-Like Peptide-1 Receptor Agonists in the Treatment of Idiopathic Inflammatory Myopathy: From Mechanisms of Action to Clinical Applications

Idiopathic inflammatory myopathies (IIMs) result in proximal muscle weakness and other intramuscular and extramuscular manifestations. Pharmacologic treatments in use for IIMs are limited to corticosteroids and immunosuppressants in addition to supportive physical and occupational therapy. Glucagon-like peptide-1 receptor (GLP-1R) agonists are currently utilized in the treatment of type II diabetes and obesity but may play a role in the treatment of IIMs. The current scoping review of extant literature aims to synthesize findings from studies assessing the therapeutic effects of GLP-1R agonists in the management of inflammatory myopathy and muscle atrophy. A literature search was conducted through PubMed, resulting in a total of 19 research-based articles included in this review. Mice and human studies showed, with varying levels of significance, that GLP-1R agonists led to decreases in muscle atrophy, inflammation, adiposity, and weakness; improvement in muscle microvasculature and endurance; and promotion of muscle mitochondria biogenesis. The potential for GLP-1R agonists to improve muscle function and architecture underscores the need for large randomized controlled, clinically comparative trials of GLP-1R agonists in patients with IIM.

Glucagon-like peptide-1 analog therapy in rare genetic diseases: monogenic obesity, monogenic diabetes, and spinal muscular atrophy

AIM

Implementing genetic analyses have unraveled rare alterations causing early-onset obesity and complications, in whom treatment is challenging. We aimed to report on the effects of adjuvant off-label therapy with liraglutide, glucagon-like peptide-1 analogue (GLP-1a), in rare genetic diagnoses.

METHODS

Case scenarios and review of the literature.

RESULTS

Case 1: Nine-year-old boy with early-onset severe obesity and nonalcoholic fatty liver disease (NAFLD) due to a homozygous mutation in the MC4R gene deteriorated under lifestyle change and metformin therapy [at 10.5 years: body mass index (BMI) 51.2kg/m², 226% of the 95th percentile, fat percentage (FP) 65% and muscle-to-fat ratio (MFR) z-score of -2.41]. One year of liraglutide treatment halted progressive weight gain [BMI 50.3kg/m², 212% of the 95th percentile, 63.7% FP and MFR z-score of -2.34], with biochemical improvement. Case 2: Twelve-year-old boy with obesity presented with diabetes and progressive NAFLD. Exome analysis revealed two heterozygous mutations compatible with monogenic diabetes (HNF1A) and familial hypercholesterolemia (LDLR). Lifestyle modifications resulted in clinical and laboratory improvement (BMI 87th percentile, 32.8% FP, MFR z-score of -1.63, HbA1c 5.5%) without the expected recovery in liver transaminases. Liraglutide treatment augmented the improvement in weight status (BMI 68th percentile, 22.6% FP, MFR z-score of -1.13) with normalization of liver transaminases. Case 3: Nineteen-year-old male with spinal muscular atrophy type 3 presented with sarcopenic obesity and comorbidities. Treatment strategy included dietary counseling and multiple drug therapies (metformin, anti-hypertensive and statins). Liraglutide therapy led to a gradual recovery of metabolic complications allowing tapering-down other medications.

CONCLUSIONS

Considering the pleiotropic effects of GLP1-a beyond BMI reduction, this treatment modality may serve as a game changer in challenging cases.

Relationships among Postprandial Plasma Active GLP-1 and GIP Excursions, Skeletal Muscle Mass, and Body Fat Mass in Patients with Type 2 Diabetes Treated with Either Miglitol, Sitagliptin, or Their Combination: A Secondary Analysis of the MASTER Study

BACKGROUND

We previously conducted a pilot randomized controlled trial "the MASTER study" and demonstrated that alpha-glucosidase inhibitor miglitol and a dipeptidyl peptidase-4 inhibitor sitagliptin modified postprandial plasma excursions of active glucagon-like peptide-1 (aGLP-1) and active gastric inhibitory polypeptide (aGIP), and miglitol treatment decreased body fat mass in patients with type 2 diabetes (T2D). However, the details regarding the relationships among postprandial plasma aGLP-1 and aGIP excursions, skeletal muscle mass, and body fat mass are unclear.

METHODS

We conducted a secondary analysis of the relationships among skeletal muscle mass index (SMI), total body fat mass index (TBFMI), and the incremental area under the curves (iAUC) of plasma aGLP-1 and aGIP excursions following mixed meal ingestion at baseline and after 24-week add-on treatment with either miglitol alone, sitagliptin alone, or their combination in T2D patients.

RESULTS

SMI was not changed after the 24-week treatment with miglitol and/or sitagliptin. TBFMI was reduced and the rates of aGIP-iAUC change were lowered in the two groups treated with miglitol, although their correlations did not reach statistical significance. We observed a positive correlation between the rates of aGIP-iAUC and TBFMI changes and a negative correlation between the rates of TBFMI and SMI changes in T2D patients treated with sitagliptin alone whose rates of aGIP-iAUC change were elevated.

CONCLUSIONS

Collectively, although T2D patients treated with miglitol and/or sitagliptin did not show altered SMI after 24-week treatment, the current study suggests that there are possible interrelationships among postprandial plasma aGIP excursion modified by sitagliptin, skeletal muscle mass, and body fat mass.

Mechanism for exercise-mediated prevention against muscle wasting on extensor digitorum longus muscle in Spontaneously Diabetic Torii fatty rats

We previously reported the significant increase in limb muscle strength and cross-sectional area of the type IIb muscle fibers in the extensor digitorum longus (EDL) muscle in a type 2 diabetic animal model, with Spontaneously Diabetic Torii (SDT) fatty rats (n = 6) undergoing regular treadmill exercise from 8 to 16 weeks of age compared with sedentary SDT fatty rats (n = 6). This study investigated the mechanism by which exercise training prevented skeletal muscle wasting in the EDL muscle of the SDT fatty rats. The endurance exercise for 8 weeks downregulated the expression of muscle RING-finger protein-1 (an E3 ubiquitin ligase) and upregulated the expression of CD31, insulin receptor substrate-2, and phosphorylated endothelial nitric oxide synthase in the EDL muscle of 16-week-old SDT fatty rats.Endurance exercise training might reduce muscle wasting by preventing muscle degradation and increasing the angiogenic response in the EDL muscle in type 2 diabetes.

Glucagon-like peptide-1 receptor agonist, liraglutide, attenuated retinal thickening in spontaneously diabetic Torii fatty rats

BACKGROUND

This study aims to investigate the effect of the glucagon-like peptide-1 (GLP-1) receptor agonist (GLP-1RA) liraglutide on retinal pathological findings as compared with insulin and hydralazine using an animal model of type 2 diabetes with obesity, hypertension, and hyperlipidemia.

METHODS

Male spontaneously diabetic Torii (SDT) fatty rats at 8 weeks of age were randomly assigned to three groups: the liraglutide group (SDT-lira, n = 6) received a subcutaneous injection of liraglutide from the age of 8 to 16 weeks, the SDT-ins-hyd group (n = 6) was provided both insulin against hyperglycemia and hydralazine against hypertension to match levels of both blood glucose and blood pressure to those of the liraglutide group, and the control group of SDT fatty rats (SDT-vehicle, n = 7) and a nondiabetic control group of Sprague-Dawley rats (SD, n = 7) were injected with vehicle only. Both eyeballs of all groups were collected at the age of 16 weeks.

RESULTS

Retinal thickness, which was found in the SDT-vehicle group, was significantly prevented to similar levels in both the SDT-lira and SDT-ins-hyd groups. Immunohistological analysis revealed that GLP-1 receptor was not expressed in the retina of all rats. The ocular protein expression of monocyte chemoattractant protein-1, which causes a proinflammatory situation, was significantly upregulated in all SDT fatty rats as compared to SD rats, but the expression levels were similar between all SDT fatty rats. With regard to neovascularization in the eyes, there were no significant differences in protein expressions of vascular endothelial growth factor, CD31, or endothelial nitric oxide synthase in all rats.

CONCLUSIONS

The present study indicates that liraglutide prevents retinal thickening, dependent on blood glucose and blood pressure levels in SDT fatty rats without ocular neovascularization. However, the effects did not improve the ocular proinflammatory state.