"Sex hormone independent associations between insulin resistance and thyroid status -a gender based biochemical study on clinically euthyroid non-obese, overweight and obese type 2 diabetics''

Sex-dependent obesogenic effect of tetracycline on Drosophila melanogaster deteriorated by dysrhythmia

Antibiotics have been identified as obesogens contributing to the prevalence of obesity. Moreover, their environmental toxicity shows sex dependence, which might also explain the sex-dependent obesity observed. Yet, the direct evidence for such a connection and the underlying mechanisms remain to be explored. In this study, the effects of tetracycline, which is a representative antibiotic found in both environmental and food samples, on Drosophila melanogaster were studied with consideration of both sex and circadian rhythms (represented by the eclosion rhythm). Results showed that in morning-eclosed adults, tetracycline significantly stimulated the body weight of females (AM females) at 0.1, 1.0, 10.0 and 100.0 µg/L, while tetracycline only stimulated the body weight of males (AM males) at 1.0 µg/L. In the afternoon-eclosed adults, tetracycline significantly stimulated the body weight of females (PM females) at 0.1, 1.0 and 100.0 µg/L, while it showed more significant stimulation in males (PM males) at all concentrations. Notably, the stimulation levels were the greatest in PM males among all the adults. The results showed the clear sex dependence of the obesogenic effects, which was diminished by dysrhythmia. Further biochemical assays and clustering analysis suggested that the sex- and rhythm-dependent obesogenic effects resulted from the bias toward lipogenesis against lipolysis. Moreover, they were closely related to the preference for the energy storage forms of lactate and glucose and also to the presence of excessive insulin, with the involvement of glucolipid metabolism. Such relationships indicated potential bridges between the obesogenic effects of pollutants and other diseases, e.g., cancer and diabetes.

The Relationship between Thyroid-Stimulating Hormone and Insulin Resistance in Incipient Elderly Type 2 Diabetics with Normal Thyroid Function

Objective

To explore correlations between serum thyroid-stimulating hormone (TSH) concentration within the normal range and insulin resistance and its possible mechanism in incipient type 2 diabetes in elderly patients.

Methods

453 elderly patients with type 2 diabetes were divided into four groups by the quartile of TSH. Body mass index (BMI), waist-to-hip ratio (WHR), fasting plasma glucose (FPG), fasting insulin (FINS), homeostasis model assessment of insulin resistance (HOMA-IR) and homeostasis model assessment of insulin secretion (HOMA-β), blood lipids, and other indicators were compared among all groups, and correlation and regression analysis were conducted. 3T3-L1 preadipocytes were induced into mature adipocytes in vitro, and different concentrations of bovine TSH were used to stimulate adipocytes. The levels of TNF-α in the culture medium were detected by ELISA.

Results

(1) With the increase of TSH, TC showed an increasing trend. Compared with the G1 group (4.80 ± 1.08), G2 group (5.13 ± 1.16), G3 group (5.14 ± 1.39), and G4 group (5.38 ± 1.16), the difference was statistically significant (P < 0.05 or P < 0.01). The LDL also showed an increasing trend. Compared with the G4 group (3.47 ± 0.89), the G1 (3.12 ± 0.82) and G2 groups (3.14 ± 1.05) had a lower LDL, and the difference was statistically significant (P < 0.01). The BMI increased between the G4 group (26.7 ± 3.97) and the G1 group (25.6 ± 3.54), and the difference was statistically significant (P < 0.05). (2) The serum TSH level was positively correlated with FPG, FINS, HOMA-IR, TC, and LDL (R = 0.292, 0.271, 0.394, 0.195, and 0.178, all P < 0.01). (3) TSH is the dependent variable, other indicators are independent variables, and multiple stepwise regression analysis is performed; the results show that only HOMA-IR, TC, and LDL enter the regression equation. (4) The TSH stimulated TNF-α secretion of 3T3-L1 adipocytes in a dose-dependent manner.

Conclusion

The TSH level was positively correlated with the insulin resistance and LDL in the elderly incipient type 2 diabetic patients. Higher levels of TSH may be involved in the development of insulin resistance in the elderly incipient type 2 diabetic patients.