Doxycycline in Extremely Low Dose Improves Glycemic Control and Islet Morphology in Mice Fed a High-Fat Diet

Mitigation of Insulin Resistance by Natural Products from a New Class of Molecules, Membrane-Active Immunomodulators

Insulin resistance (IR), accompanied by an impaired cellular glucose uptake, characterizes diverse pathologies that include, but are not limited to, metabolic disease, prediabetes and type 2 diabetes. Chronic inflammation associated with deranged cellular signaling is thought to contribute to IR. The key molecular players in IR are plasma membrane proteins, including the insulin receptor and glucose transporter 4. Certain natural products, such as lipids, phenols, terpenes, antibiotics and alkaloids have beneficial effects on IR, yet their mode of action remains obscured. We hypothesized that these products belong to a novel class of bioactive molecules that we have named membrane-active immunomodulators (MAIMs). A representative MAIM, the naturally occurring medium chain fatty acid ester diethyl azelate (DEA), has been shown to increase the fluidity of cell plasma membranes with subsequent downstream effects on cellular signaling. DEA has also been shown to improve markers of IR, including blood glucose, insulin and lipid levels, in humans. The literature supports the notion that DEA and other natural MAIMs share similar mechanisms of action in improving IR. These findings shed a new light on the mechanism of IR mitigation using natural products, and may facilitate the discovery of other compounds with similar activities.

Drug-induced mitochondrial toxicity: Risks of developing glucose handling impairments

Mitochondrial impairment has been associated with the development of insulin resistance, the hallmark of type 2 diabetes mellitus (T2DM). However, the relationship between mitochondrial impairment and insulin resistance is not fully elucidated due to insufficient evidence to support the hypothesis. Insulin resistance and insulin deficiency are both characterised by excessive production of reactive oxygen species and mitochondrial coupling. Compelling evidence states that improving the function of the mitochondria may provide a positive therapeutic tool for improving insulin sensitivity. There has been a rapid increase in reports of the toxic effects of drugs and pollutants on the mitochondria in recent decades, interestingly correlating with an increase in insulin resistance prevalence. A variety of drug classes have been reported to potentially induce toxicity in the mitochondria leading to skeletal muscle, liver, central nervous system, and kidney injury. With the increase in diabetes prevalence and mitochondrial toxicity, it is therefore imperative to understand how mitochondrial toxicological agents can potentially compromise insulin sensitivity. This review article aims to explore and summarise the correlation between potential mitochondrial dysfunction caused by selected pharmacological agents and its effect on insulin signalling and glucose handling. Additionally, this review highlights the necessity for further studies aimed to understand drug-induced mitochondrial toxicity and the development of insulin resistance.

Associations of typical antibiotic residues with elderly blood lipids and dyslipidemia in West Anhui, China

Growing evidence has indicated the association of clinical antibiotic use with abnormal blood lipid levels; however, no epidemiological study has examined the relationship of antibiotic exposure, probably derived from food chains, with blood lipid levels. This study investigated the relationships of urinary antibiotic levels with blood lipid levels and dyslipidemias in the older population. Baseline data of 960 participants from the Cohort of Elderly Health and Environment Controllable Factors were used in the present study. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was performed to detect antibiotic residues in the urine samples of the participants. Our findings revealed that each 1 μg/g increase in enrofloxacin and ciprofloxacin levels was associated with an increase of 0.084 (95 % confidence interval (CI): 0.030, 0.139) and 0.049 (95 % CI: 0.012, 0.086) in triglyceride levels, respectively. Enrofloxacin was associated with an increased risk of hypertriglyceridemia. Each 1 μg/g increase in the enrofloxacin level corresponded to an increase of 0.052 (95 % CI: 0.006, 0.098) in the low-density lipoprotein cholesterol level. Furthermore, florfenicol exposure increased the risks of both hyperbetalipoproteinemia and hypoalphalipoproteinemia. By contrast, each 1 μg/g increase in sulfaclozine and doxycycline levels was associated with a - 0.062 (95 % CI: -0.111, -0.020), and - 0.083 (95 % CI: -0.160, -0.007) decrease in total cholesterol levels, respectively. Sulfaclozine was closely related to a decreased risk of hypercholesterolemia. Stratification analysis revealed specific differences in the correlation between antibiotic exposure and lipid levels based on the waist circumference (WC) values of the participants. Except for sulfaclozine and doxycycline, other antibiotics exerted adverse effects on lipid levels and increased dyslipidemia prevalence. The older participants with higher WC values were vulnerable to antibiotic exposure. Therefore, an appropriate understanding of the epidemiological attributes of antibiotic residues is indispensable to prevent abdominal obesity in the older population.

Typical antibiotic exposure and dysglycemia risk in an elderly Chinese population

Studies examined the connection between antibiotic exposure in urine and dysglycemia risk (including prediabetes and diabetes) in the elderly were limited. Multiple linear regression, binary logistic regression, restricted cubic splines (RCS), and stratified analysis were applied to analyze the relationship between antibiotic exposure and dysglycemia risk. We observed that sulfaclozine exposure 0.07 (95% confidence interval [CI]: 0.01-0.23) significantly increased fasting blood glucose (FBG) level. By mechanism, usage, and antimicrobial action, sulfonamides 0.08 (95% CI: 0.06-0.36), veterinary antibiotics (VA) 0.07 (95% CI: 0.01-0.30), or bacteriostatic antibiotics 0.07 (95% CI: 0.02-0.29) significantly increased FBG level. Additionally, sulfaclozine exposure 1.54 (95% CI: 1.02-2.33) resulted in a higher dysglycemia risk, while doxycycline exposure 0.53 (95% CI: 0.30-0.95) resulted in a lower dysglycemia risk. By mechanism, usage, and antimicrobial action, sulfonamides 1.44 (95% CI: 1.02-2.04), VA 1.68 (95% CI: 1.21-2.35), or bacteriostatic antibiotics 1.40 (95% CI: 1.02-1.93) exposure had a higher dysglycemia risk. Taken together, exposure to sulfonamides, VA, especially sulfaclozine, was correlated with a higher dysglycemia risk in the elderly. Exposure to bacteriostatic antibiotics was associated with a higher dysglycemia risk in the female.

The Antibiotic Doxycycline Impairs Cardiac Mitochondrial and Contractile Function

Tetracycline antibiotics act by inhibiting bacterial protein translation. Given the bacterial ancestry of mitochondria, we tested the hypothesis that doxycycline-which belongs to the tetracycline class-reduces mitochondrial function, and results in cardiac contractile dysfunction in cultured H9C2 cardiomyoblasts, adult rat cardiomyocytes, in Drosophila and in mice. Ampicillin and carbenicillin were used as control antibiotics since these do not interfere with mitochondrial translation. In line with its specific inhibitory effect on mitochondrial translation, doxycycline caused a mitonuclear protein imbalance in doxycycline-treated H9C2 cells, reduced maximal mitochondrial respiration, particularly with complex I substrates, and mitochondria appeared fragmented. Flux measurements using stable isotope tracers showed a shift away from OXPHOS towards glycolysis after doxycycline exposure. Cardiac contractility measurements in adult cardiomyocytes and Drosophila melanogaster hearts showed an increased diastolic calcium concentration, and a higher arrhythmicity index. Systolic and diastolic dysfunction were observed after exposure to doxycycline. Mice treated with doxycycline showed mitochondrial complex I dysfunction, reduced OXPHOS capacity and impaired diastolic function. Doxycycline exacerbated diastolic dysfunction and reduced ejection fraction in a diabetes mouse model vulnerable for metabolic derangements. We therefore conclude that doxycycline impairs mitochondrial function and causes cardiac dysfunction.