The Influence of Clinically Diagnosed Neuropathy on Respiratory Muscle Strength in Type 2 Diabetes Mellitus

Changes in phrenic nerve compound muscle action potential in streptozotocin-induced diabetic rats

PURPOSE

To evaluate the phrenic nerve compound muscle action potential (CMAP) in rats after diabetes mellitus (DM) induction.

METHODS

Twenty DM animals (intravenous streptozotocin, 45 mg.kg^-1) and 25 controls underwent CMAP analysis before and 30, 60 and 90 days after DM induction.

RESULTS

Amplitude (mV) progressively declined in DM group after 30 (Mean difference (MD): -0.915, 95 % Confidence interval (CI) -1.580 to -0.250, p < 0.01), 60 (MD: -1.122, 95 % CI -1.664 to -0.581, p < 0.001) and 90 days (MD: -2.226, 95 % CI -3.059 to -1.393, p < 0.001); as well as the area (mV.ms) after 30 (MD: -3.19, 95 % CI -5.94 to -0.44, p < 0.05), 60 (MD: -3.94, 95 % CI -6.24 to -1.64, p < 0.001) and 90 days (MD: -8.64, 95 % CI -12.08 to -5.21, p < 0.001). Transient differences were observed in latency and duration at 60 days.

CONCLUSIONS

The progressive changes in phrenic nerve CMAP observed during DM suggest a decrement in axonal function rather than substantial demyelination.

Type 2 Diabetes Mellitus Related to Decreased Peripheral and Respiratory Muscle Strength in Sarcopenic Thai Elderly

BACKGROUND

Age is related to a decline in muscle mass and physical function in both respiratory and peripheral muscle strength, which could lead to mobility and mortality. In addition, older people have suffered from one or multiple chronic conditions in particular in type 2 Diabetes Mellitus (type 2 DM). However, a few studies have reported the relationship between sarcopenic elderly and respiratory and peripheral muscle strengths in type 2DM.

OBJECTIVE

To explore the prevalence of sarcopenia in type 2 DM elderly people among community- dwelling patients and the relationships with peripheral and respiratory muscle loss in sarcopenic type 2 DM older patients.

METHODS

A total of 330 older individuals were recruited from community-dwelling centers. Respiratory muscle and quadriceps muscle were assessed. According to the defined criteria for sarcopenia (defined by Asian Working Group for Sarcopenia), muscle mass, gait speed (six-meter walk test), and handgrip strength were examined.

RESULTS

Of 330 elderly people, 82 volunteers had a history of type 2 DM. Participants with type 2DM had a risk for sarcopenia (odds ratio= 2.324, 95% CI=1.251-4.317). The prevalence of sarcopenia was 25.61% among older participants with type 2 DM. In addition, decreased respiratory muscle strength and quadriceps muscle strength were observed in type 2 DM with sarcopenia compared to type 2 DM with non-sarcopenia. These relationships also remained after controlling for age and sex.

CONCLUSION

Sarcopenia in type 2 DM leads to a decrease in respiratory muscle and peripheral muscle strength.

Pulmonary function tests in type 2 diabetes: a meta-analysis

OBJECTIVES

The aim of this study was to determine the association between type 2 diabetes (T2D) and pulmonary function tests.

METHODS

After conducting an exhaustive literature search, we performed a meta-analysis. We employed the inverse variance method with a random-effects model to calculate the effect estimate as the mean difference (MD) and 95% confidence interval (CI). We calculated the heterogeneity with the I2 statistic and performed a meta-regression analysis by sex, body mass index (BMI), smoking and geographical region. We also conducted a sensitivity analysis according to the studies' publication date, size of the T2D group and the study quality, excluding the study with the greatest weight in the effect.

RESULTS

The meta-analysis included 66 studies (one longitudinal, two case-control and 63 cross-sectional), with 11 134 patients with T2D and 48 377 control participants. The pooled MD (95% CI) for the predicted percentage of forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), forced expiratory flow at 25-75% of FVC, peak expiratory flow, and diffusing capacity of the lung for carbon monoxide were -7.15 (95% CI -8.27, -6.03; p<0.001), -9.21 (95% CI -11.15, -7.26; p<0.001), -9.89 (95% CI -14.42, -5.36; p<0.001), -9.79 (95% CI -13.42, -6.15; p<0.001) and -7.13 (95% CI -10.62, -3.64; p<0.001), respectively. There was no difference in the ratio of FEV1/FVC (95% CI -0.27; -1.63, 1.08; p=0.69). In all cases, there was considerable heterogeneity. The meta-regression analysis showed that between studies heterogeneity was not explained by patient sex, BMI, smoking or geographical region. The findings were consistent in the sensitivity analysis.

CONCLUSIONS

T2D is associated with impaired pulmonary function, independently of sex, smoking, BMI and geographical region. Longitudinal studies are needed to investigate outcomes for patients with T2D and impaired pulmonary function.

Analysis of the Molecular Signaling Signatures of Muscle Protein Wasting Between the Intercostal Muscles and the Gastrocnemius Muscles in db/db Mice

Type 2 diabetes (T2D) patients suffer from dyspnea, which contributes to disease-related morbidity. Although T2D has been reported to induce a catabolic state in skeletal muscle, whether T2D induces muscle wasting in respiratory muscles has not yet been investigated. In this study, we examine the difference in the molecular signaling signature of muscle wasting between the intercostal and gastrocnemius muscles using db/db mice, a well-known diabetic mouse model. Akt phosphorylation was significantly decreased in both the intercostal and gastrocnemius muscles of db/db mice and was accompanied by a decrease in mTORC1 activity. In addition, FoxO phosphorylation was suppressed, and ubiquitin-proteasome degradation, characterized by the level of Atrogin-1 and MuRF1, was subsequently enhanced in both muscle types of db/db mice. An increase in LC3BII levels and a decrease in p62 levels marked the occurrence of substantial autophagy in the gastrocnemius muscle but not in the intercostal muscles of db/db mice. Therefore, we suggest that the signaling events of muscle wasting in the intercostal muscles of db/db mice are different from those in the gastrocnemius muscle of db/db mice.

Kaempferol protects retinal ganglion ceils from high-glucose-induced injury by regulating vasohibin-1

Kaempferol is a medicinal flavonol derived from the roots of Kaempferia galanga L. Kaempferol can affect cell survival, apoptosis, and anti-oxidation, though its role and underlying mechanism in retinal ganglion cells with high-glucose injury remains unclear. In this study, we explored kaempferol's role in high-glucose injury in cells from the retinal ganglion cell (RGC) line. RGC cells were isolated and then cultured in high glucose (55 mmol/L) for 0 h, 12 h, 24 h, 48 h, or 72 h, and results showed decreased cell viability at 48 h and 72 h. We treated RGC cells with different concentrations of kaempferol (0 μmol/L, 20 μmol/L, 40 μmol/L, 60 μmol/L, 80 μmol/L, or 100 μmol/L) and high-glucose (55 mmol/L) for 48 h. The data indicated inhibited lactate dehydrogenase leakage, apoptosis, caspase-3 activity, and reactive oxygen species (ROS) levels. Moreover, whereas cell viability increased in RGC cells that were incubated with kaempferol (60 μmol/L, 80 μmol/L, or 100 μmol/L) and glucose (55 mmol/L), compared with glucose alone. Kaempferol (60 μmol/L) elevated ERK phosphorylation and vasohibin-1 (VASH1) expression, and inhibition of ERK phosphorylation reversed the effect of kaempferol (60 μmol/L) on VASH1 expression in RGC cells with high-glucose injury. Additionally, interference of VASH1 by VASH1 siRNA markedly reversed the effects of kaempferol (60 μmol/L) on cell viability, caspase-3 activity, and ROS levels in RGC cells with high glucose injury. Taken together, the results suggest that kaempferol protected retinal ganglion cells from high-glucose-induced injury via ERK and VASH1 signaling.