We examined muscle activation during low-intensity muscle contractions with a moderate restriction of blood flow and complete occlusion of blood flow. Unilateral elbow flexion muscle contractions (20% of 1-RM) were performed in Experiment 1 (30 contractions), Experiment 2 (3 sets x 10 contractions), and Experiment 3 (30 repetitive contractions followed by 3 sets x 15 contractions) with moderate restriction, complete occlusion of blood flow or unrestricted blood flow (control). Electromyography (EMG) was recorded from surface electrodes placed on the biceps brachii muscle and the integrated EMG (iEMG) and mean power frequency (MPF) obtained. During Experiments 1 and 2, muscle activation was progressively increased in complete occlusion and moderate restriction of blood flow to levels greater than in the control. The decline in maximal voluntary isometric contraction (MVC) following the bout of contractions was greater with complete occlusion (39-48%) than moderate restriction of blood flow (16-19%); control MVC did not change. In Experiment 3, changes in MVC, iEMG, and MPF were greater with moderate restriction of blood flow than in the control but comparable with complete occlusion of blood flow where less total work was performed. In conclusion, moderate restriction of blood flow results in similar neural manifestations in muscle as complete occlusion of blood flow but without the apparent contractile/metabolic impairment observed with complete occlusion. Thus, low-intensity muscle contractions, with moderate restriction of blood flow, leads to more intense activation of the muscle relative to the external load.

Although the accumulation of advanced glycation end-products (AGEs) of the Maillard reaction in our body is reported to increase with aging and is enhanced by the pathogenesis of lifestyle-related diseases such as diabetes, routine measurement of AGEs is not applied to regular clinical diagnoses due to the lack of conventional and reliable techniques for AGEs analyses. In the present study, a non-invasive AGEs measuring device was developed and the association between skin AGEs and diabetic complications was evaluated. To clarify the association between the duration of hyperglycemia and accumulation of skin fluorophores, diabetes was induced in mice by streptozotocin. As a result, the fluorophore in the auricle of live mice was increased by the induction of diabetes. Subsequent studies revealed that the fingertip of the middle finger in the non-dominant hand is suitable for the measurement of the fluorescence intensity by the standard deviation value. Furthermore, the fluorescence intensity was increased by the presence of diabetic microvascular complications. This study provides the first evidence that the accumulation of fluorophore in the fingertip increases with an increasing number of microvascular complications, demonstrating that the presence of diabetic microvascular complications may be predicted by measuring the fluorophore concentration in the fingertip.

Approximately 100 years have passed since the Maillard reaction was first reported in the field of food chemistry as a condensation reaction between reducing sugars and amino acids. This reaction is thought to progress slowly primarily from glucose with proteins in vivo. An early-stage product, called the ”Amadori product”, is converted into advanced glycation end products. Those accumulate in the body in accordance with age, with such accumulation being enhanced by lifestyle-related diseases that result in the denaturation of proteins. Recent studies have demonstrated that intermediate carbonyls are generated by several pathways, and rapidly generate many glycation products. However, accurate quantification of glycation products in vivo is difficult due to instability and differences in physicochemical properties. In this connection, little is known about the relationship between the structure of glycation products and pathology. Furthermore, the interaction between proteins modified by glycation and receptors for advanced glycation end products is also known to induce the production of several inflammatory cytokines. Therefore, those inhibitors have been developed over the world to prevent lifestyle-related diseases. In this review, we describe the process of protein denaturation induced by glycation and discuss the possibility of using the process as a marker of age-related diseases.

Imeglimin, a tetrahydrotriazine anti-hyperglycemic agent, is thought to have effects on mitochondrial function of the liver, skeletal muscle, and pancreatic β-cells. However, the molecular mechanisms of imeglimin action have been still unclear. Treatment of mouse islets with 1.0 mM imeglimin significantly increased insulin release in response to glucose (2.1-fold, p<0.01 at 11.1 mM glucose; 1.9-fold, p<0.05 at 16.7 mM glucose, compared to 3.9 mM glucose). Treatment with a combination of liraglutide (100 nM) and imeglimin did not show an additional increase in insulin secretion compared to the treatment with liraglutide alone. Liraglutide and imeglimin significantly increased EdU-incorporated proliferating β-cells in the islets under 11.1 mM glucose (1.02% in vehicle control; 2.21% in liraglutide, p<0.01 vs. vehicle; 1.46% in 1.0 mM imeglimin, p<0.01 vs. vehicle). Imeglimin prevented β-cell apoptosis induced by high glucose (32% of control in imeglimin, p<0.01; 57% of control in liraglutide, p=0.068). We conducted gene expression microarray analysis of islets treated with imeglimin under high glucose and some ER stress-related gene expression were altered by imeglimin. Then, we examined the effects of imeglimin on ER stress-induced β-cell apoptosis in mouse islets. Imeglimin significantly reduced β-cell apoptosis induced by thapsigargin at 5.6 mM glucose (29% of thapsigargin, p<0.01). Imeglimin further upregulated the expression of C/EBP homologous protein (CHOP) under thapsigargin treatment and tended to decrease phosphorylation of eIF2-α. We also confirmed that imeglimin improved β-cell apoptosis induced by high glucose or thapsigargin in human islets. Collectively, imeglimin prevented β-cell apoptosis induced by high glucose or thapsigargin, in addition to increase in insulin secretion and β-cell proliferation. Imeglimin seemed to regulate CHOP/GADD34-mediated dephosphorylation of eIF2-α to recover from translational inhibition. Disclosure J. Li: None. J. Shirakawa: None. Y. Togashi: None. Y. Terauchi: Advisory Panel; Self; AstraZeneca, Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novo Nordisk A/S, Sanofi. Research Support; Self; Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp & Dohme Corp., Novartis Pharmaceuticals Corporation, Novo Nordisk A/S, Ono Pharmaceutical Co., Ltd., Sanofi, Shionogi & Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd. Speaker's Bureau; Self; Astellas Pharma Inc., AstraZeneca, Bayer Yakuhin, Ltd., Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp & Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novartis Pharmaceuticals Corporation, Novo Nordisk A/S, Ono Pharmaceutical Co., Ltd., Sanofi, Sanwa Kagaku Kenkyusho, Shionogi & Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd.

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