Dwarfism and insulin resistance in male offspring caused by α1-adrenergic antagonism during pregnancy

An improved method for the precise unravelment of non-shivering brown fat thermokinetics

Since the discovery of functional brown adipose tissue (BAT) in adult humans, research on BAT gained a new popularity to combat obesity and related comorbidities. To date, however, methods to quantify BAT thermogenesis are often either highly invasive, require advanced equipment, are time consuming or of limited sensitivity. Here we present a simple yet highly effective and minimally invasive protocol for the Precise Unravelment of Non-shivering brown fat thermoKinetics (PUNK) in mice using infrared thermography in combination with Vaseline to brush up the fur between the shoulder blades. We also use physiological and molecular readouts including indirect calorimetry, qPCR and Western Blots to test our protocol. Our study demonstrates that Vaseline before thermography vastly advances the reproducibility and quality of BAT infrared pictures or videos, as it exposes the skin above the BAT for a direct line of sight for the infrared camera and thereby circumvents the well-known problems associated with shaving and anaesthesia. We subsequently validate that this approach does not affect physiological and molecular BAT function, but instead leads to more robust and less variable results when comparing for instance norepinephrine stimulation tests or knockout animals. Taken together, the PUNK protocol for BAT thermography quickly and effectively improves scientific outcomes of this method, and can be easily added to existing paradigms. Consequently, it safes money, time and experimental animals, thereby putting the 3R's principles of animal welfare into practice.

Prenatal High-Salt Diet-Induced Metabolic Disorders via Decreasing Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1α in Adult Male Rat Offspring

SCOPE

Although prenatal high-salt (HS) intake leads to physiological complications in the offspring, little is known regarding its effects on the offspring's glucose metabolism. Therefore, the objectives of this study are to determine the consequences of prenatal HS diet on the offspring's metabolism and to test a potential therapy.

METHODS AND RESULTS

Pregnant rats are fed either a normal-salt (1% NaCl) or high-salt (8% NaCl) diet during the whole pregnancy. Experiments are conducted in five-month-old male offspring. It is found that the prenatal HS diet reduced the glucose tolerance and insulin sensitivity of the offspring. Additionally, there is down-regulation of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (Ppargc1a/PPARGC1A) at the transcript and protein level, which leads to decreased mitochondrial biogenesis and oxidative respiration in skeletal muscle. Moreover, the down-regulation of Ppargc1a is accompanied by decreases in the expression of glucose transporter type 4 (Glut4). With endurance exercise training, these changes are mitigated, which ultimately resulted in improved insulin resistance.

CONCLUSION

These findings suggest that prenatal HS intake induces metabolic disorders via the decreased expression of Ppargc1a in the skeletal muscle of adult offspring, providing novel information concerning the mechanisms and early prevention of metabolic diseases of fetal origins.

Effects of sildenafil treatment on thermogenesis and glucose homeostasis in diet-induced obese mice

Stimulation of thermogenic pathways appears to be a promising approach to find new ways of tackling metabolic diseases like obesity and diabetes mellitus type 2. Thermogenic, weight reducing and insulin sensitizing effects of phosphodiesterase 5 (PDE 5) inhibitors have recently been postulated, suggesting that modulators of endogenous cGMP signaling have the therapeutic potential to treat metabolic disorders. However, most studies have been performed in vitro or in animals that were not glucose intolerant. We, thus, aimed to test the metabolic effects of the PDE 5 inhibitor sildenafil by treating diet-induced obese (DIO) mice orally for 8 days. Surprisingly, our results revealed no changes in body temperature, brown adipose tissue (BAT) thermogenesis and gene expression in BAT and inguinal white adipose tissue (iWAT), thus excluding a thermogenic or 'browning' effect of sildenafil in preexisting obesity. In contrast, sildenafil-treated DIO mice displayed changes in liver metabolism and glucose homeostasis resulting in impaired glucose tolerance (P < 0.05), demonstrating for the first time an unfavorable metabolic effect of increased hepatic cGMP signaling in obesity. As sildenafil is commonly prescribed to treat pulmonary arterial hypertension and erectile dysfunction in diabetic and/or obese patients, follow up studies are urgently required to re-evaluate the drug safety.