The roles of aerobic exercise training and suppression IL-6 gene expression by RNA interference in the development of insulin resistance. Cytokine. 2013;61:394-405. [PMID: 23294974 DOI: 10.1016/j.cyto.2012.11.027]

The Proposal of Molecular Mechanisms of Weak Organic Acids Intake-Induced Improvement of Insulin Resistance in Diabetes Mellitus via Elevation of Interstitial Fluid pH

Blood contains powerful pH-buffering molecules such as hemoglobin (Hb) and albumin, while interstitial fluids have little pH-buffering molecules. Thus, even under metabolic disorder conditions except severe cases, arterial blood pH is kept constant within the normal range (7.35~7.45), but the interstitial fluid pH under metabolic disorder conditions becomes lower than the normal level. Insulin resistance is one of the most important key factors in pathogenesis of diabetes mellitus, nevertheless the molecular mechanism of insulin resistance occurrence is still unclear. Our studies indicate that lowered interstitial fluid pH occurs in diabetes mellitus, causing insulin resistance via reduction of the binding affinity of insulin to its receptor. Therefore, the key point for improvement of insulin resistance occurring in diabetes mellitus is development of methods or techniques elevating the lowered interstitial fluid pH. Intake of weak organic acids is found to improve the insulin resistance by elevating the lowered interstitial fluid pH in diabetes mellitus. One of the molecular mechanisms of the pH elevation is that: (1) the carboxyl group (R-COO⁻) but not H⁺ composing weak organic acids in foods is absorbed into the body, and (2) the absorbed the carboxyl group (R-COO⁻) behaves as a pH buffer material, elevating the interstitial fluid pH. On the other hand, high salt intake has been suggested to cause diabetes mellitus; however, the molecular mechanism is unclear. A possible mechanism of high salt intake-caused diabetes mellitus is proposed from a viewpoint of regulation of the interstitial fluid pH: high salt intake lowers the interstitial fluid pH via high production of H⁺ associated with ATP synthesis required for the Na⁺,K⁺-ATPase to extrude the high leveled intracellular Na⁺ caused by high salt intake. This review article introduces the molecular mechanism causing the lowered interstitial fluid pH and insulin resistance in diabetes mellitus, the improvement of insulin resistance via intake of weak organic acid-containing foods, and a proposal mechanism of high salt intake-caused diabetes mellitus.

Interval aerobic training combined with strength-endurance exercise improves metabolic markers beyond caloric restriction in Zucker rats

AIMS

To investigate the effects of interval aerobic training combined with strength-endurance exercise (IASE) and caloric restriction (CR) on body composition, glycaemic and lipid profile and inflammatory markers.

METHODS AND RESULTS

Thirty-two Zucker diabetic fatty rats were randomised into 4 groups (sedentary + CR; sedentary + adlibitum; IASE + CR; and IASE + adlibitum). Training groups conducted an IASE programme in the same session, 5 days/week for 2 months. Body weight, fat and muscle mass and body water were measured using a body composition analyser. Plasma total, LDL and HDL cholesterol, phospholipids, triglycerides, insulin, adiponectin, tumour necrosis factor alpha, interleukin 1 and 10 were measured. Blood fasting and postprandial glucose were assessed. Body weight was lower in the CR compared to the adlibitum groups (p < 0.001). Fat mass was lower in the CR compared to the adlibitum (p < 0.05) and in the IASE compared to the sedentary groups (p < 0.001), but IASE increased lean mass (p < 0.001). Triglycerides were lower in the CR compared to the adlibitum groups (p < 0.001) whereas total and LDL-cholesterol and fasting glucose were reduced only in the IASE groups (all, p < 0.001). Phospholipids decreased in the CR compared to the adlibitum (p < 0.05) and the IASE compared to the sedentary groups (p < 0.001). The area under the curve after oral glucose tolerance test, insulin and homoeostatic model assessment were lower in the IASE and the CR compared to the sedentary and adlibitum groups, respectively (all, p < 0.001). Adiponectin was lower in the CR groups (p < 0.001).

CONCLUSION

Overall, IASE as well as CR were both useful interventions, especially when combined. However, IASE showed greater improvements on body composition, inflammatory and glycaemic profile than CR did.

Impact of high glucose on metastasis of colon cancer cells

AIM: To investigate the possible mechanism of how glucose promotes invasion and metastasis of colon cancer cells.

METHODS: CT-26 rat colorectal cancer cells were cultured in different concentrations of glucose environments (10, 20, and 30 mmol/L). Wound healing assay and transwell chamber invasion assay were utilized to test the migration and invasion, respectively. In order to understand the role of signal transducer and activator of transcription 3 (STAT3) in the process, STAT3 inhibitors, including Stattic (an STAT3 specific inhibitor) and small interfering RNA targeting STAT3, were used to block STAT3 function to evaluate their impact on CT-26 cell motion. To verify whether STAT3 and matrix metalloproteinase-9 (MMP-9) protein expression is associated with glucose-induced cell movement, Western blot was used to compare the differences in the expression of MMP-9 and STAT3 in cells incubated with and without STAT3 inhibitors in high glucose condition.

RESULTS: In both wound healing and invasion assays, the migration and invasion of CT-26 cells increased gradually with the increase in glucose concentration. However, the glucose-induced migration and invasion were obviously inhibited by STAT3 inhibitors (P < 0.05). Similarly, in Western blot assessment, both MMP-9 and STAT3 expression increased under a high glucose environment and the highest expression was achieved when 30 mmol/L glucose was used. However, in cells treated with 30 mmol/L mannitol, either MMP-9 or STAT3 expression did not increase (P > 0.05). When STAT3 inhibitors were added in the 30 mM glucose group, not only STAT3 but also MMP-9 expression decreased significantly (P < 0.05).

CONCLUSION: Our study provides evidence that glucose can promote both migration and invasion of CT-26 cells, and that the STAT3-induced MMP-9 signal pathway is involved in this process.