Alessandro Rubini

Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets

Very-low-carbohydrate diets or ketogenic diets have been in use since the 1920s as a therapy for epilepsy and can, in some cases, completely remove the need for medication. From the 1960s onwards they have become widely known as one of the most common methods for obesity treatment. Recent work over the last decade or so has provided evidence of the therapeutic potential of ketogenic diets in many pathological conditions, such as diabetes, polycystic ovary syndrome, acne, neurological diseases, cancer and the amelioration of respiratory and cardiovascular disease risk factors. The possibility that modifying food intake can be useful for reducing or eliminating pharmaceutical methods of treatment, which are often lifelong with significant side effects, calls for serious investigation. This review revisits the meaning of physiological ketosis in the light of this evidence and considers possible mechanisms for the therapeutic actions of the ketogenic diet on different diseases. The present review also questions whether there are still some preconceived ideas about ketogenic diets, which may be presenting unnecessary barriers to their use as therapeutic tools in the physician’s hand.

Flow and Volume Dependence of Rat Airway Resistance During Constant Flow Inflation and Deflation

Study ObjectivesThe aim of this study was to measure the flow and volume dependence of both the ohmic and the viscoelastic pressure dissipations of the normal rat respiratory system separately during inflation and deflation.MethodThe study was conducted in the Respiratory Physiology Laboratory in our institution. Measurements were obtained for Seven albino Wistar rats of both sexes by using the flow interruption method during constant flow inflations and deflations. Measurements included anesthesia induction, tracheostomy and positioning of a tracheal cannula, positive pressure ventilation, constant flow respiratory system inflations and deflations at two different volumes and flows.ResultsThe ohmic resistance exhibited volume and flow dependence, decreasing with lung volume and increasing with flow rate, during both inflation and deflation. The stress relaxation-related viscoelastic resistance also exhibited volume and flow dependence. It decreased with the flow rate at a constant lung volume during both inflation and deflation, but exhibited a different behavior with the lung volume at a constant flow rate (i.e., increased during inflations and decreased during deflations). Thus, stress relaxation in the rat lungs exhibited a hysteretic behavior.ConclusionsThe observed flow and volume dependence of respiratory system resistance may be predicted by an equation derived from a model of the respiratory system that consists of two distinct compartments. The equation agrees well with the experimental data and indicates that the loading time is the critical parameter on which stress relaxation depends, during both lung inflation and deflation.

The effect of body cooling on respiratory system mechanics and hysteresis in rats

Literature reports and theoretical considerations suggest that body cooling may affect respiratory mechanics in vivo. To examine this hypothesis, healthy rats were studied using the end-inflation occlusion method under control conditions and after total body cooling. Respiratory mechanics parameters, hysteresis areas, the inspiratory work of breathing, and its elastic and resistive components, were calculated. After body cooling (mean rectal temperature from 36.6 ± 0.25 to 32.1 ± 0.26 °C), the ohmic and the additional visco-elastic respiratory system resistances, the hysteresis, the total inspiratory work of breathing, and its resistive components, were all increased. No significant changes were detected for the static and dynamic respiratory system elastance mean values, and the related elastic component of the work of breathing. These data indicate that body cooling increases the mechanical inspiratory work of breathing by increasing the resistive pressures dissipation. This effect is evident even for limited temperature variations, and it is suggested that it may occur in the event of accidental or therapeutic hypothermia.

The Effect of Acute Exposure to Hyperbaric Oxygen on Respiratory System Mechanics in the Rat

PurposeThis study was designed to investigate the possible effects of acute hyperbaric hyperoxia on respiratory mechanics of anaesthetised, positive-pressure ventilated rats.MethodsWe measured respiratory mechanics by the end-inflation occlusion method in nine rats previously acutely exposed to hyperbaric hyperoxia in a standard fashion. The method allows the measurements of respiratory system elastance and of both the “ohmic” and of the viscoelastic components of airway resistance, which respectively depend on the newtonian pressure dissipation due to the ohmic airway resistance to air flow, and on the viscoelastic pressure dissipation caused by respiratory system tissues stress–relaxation. The activities of inducible and endothelial NO-synthase in the lung’s tissues (iNOS and eNOS respectively) also were investigated. Data were compared with those obtained in control animals.ResultsWe found that the exposure to hyperbaric hyperoxia increased respiratory system elastance and both the “ohmic” and viscoelastic components of inspiratory resistances. These changes were accompanied by increased iNOS but not eNOS activities.ConclusionsHyperbaric hyperoxia was shown to acutely induce detrimental effects on respiratory mechanics. A possible causative role was suggested for increased nitrogen reactive species production because of increased iNOS activity.

The effect of angiotensin-converting enzyme inhibition by captopril on respiratory mechanics in healthy rats.

Context: Angiotensin stimulates smooth-muscle contraction. Accordingly, angiotensin-converting enzyme (ACE) inhibition is expected to decrease airway resistance. Objectives: To measure the effects of ACE inhibition on respiratory mechanics in healthy mammals. Materials and methods: We measured respiratory mechanics before and after i.p. ACE inhibitor captopril (100u2009mg/kg) in normal anaesthetised rats. The end-inflation occlusion method allowed the measurements of respiratory system elastance and ohmic and viscoelastic pressure dissipations. Respiratory system hysteresis and the elastic and resistive work of breathing were calculated. Results: Captopril induced a reduction of the ohmic and the total respiratory system resistances, while respiratory system hysteresis and elastance did not change. Accordingly, a reduction of the resistive and of the total work of breathing was observed. Conclusions: The captopril-induced reduction of airway resistance indicates that angiotensin modulates bronchomotor tone in basal conditions. ACE inhibition may positively affect respiratory system mechanics and work of breathing.

Body metabolic rate and electromyographic activities of antigravitational muscles in supine and standing postures

We measured metabolic (oxygen uptake, carbon dioxide production, respiratory ratio), cardio-circulatory (heart rate, systolic and diastolic arterial blood pressure, rate-pressure product, an index of myocardial oxygen consumption calculated by multiplying heart rate by systolic pressure) and electromyographic (integrated electromyographic activities of two antigravitational muscles of the lower limb, soleus and gastrocnemius) variables on 12 young healthy subjects in supine and standing positions at rest. We found statistically significant increments of oxygen uptake, carbon dioxide production, heart rate and integrated electromyographic activities in standing versus supine position. Rate-pressure product increased but not significantly, and no other significant changes were detected. We conclude that postural changes influence metabolic rate, antigravitational muscle reflex activities, and heart rate. A significant positive correlation was found between oxygen uptake and carbon dioxide production and integrated electromyographic activities of antigravitational muscles, while the same was not found for cardio-circulatory variables. These results suggest that the increased metabolic rate in standing position is, at least in part, due to antigravitational muscle tone.

Hippocampal cellular loss after brief hypotension

Brief episodes of hypotension have been shown to cause acute brain damage inanimal models. We used a rat hemorrhagic shock model to assess functionaloutcome and to measure the relative neuronal damage at 1, 4 and 14 dayspost-injury (3 min of hypotension). All rats underwent a neurological assessmentincluding motor abilities, sensory system evaluation and retrograde memory atpost-hypotensive insult. Brains were harvested and stained for Fluorojade C andNissl. Stereology was used to analyze Fluorojade C and Nissl stained brainsections to quantitatively detect neuronal damage after the hypotensive insult.Statistical analysis was performed using Graphpad Prism 5 with the Bonferronitest at a 95% confidence interval after ANOVA. A Mixed Effect Model was usedfor the passive avoidance evaluation. Stereologically counted fluorojadepositive cells in the hippocampus revealed significant differences in neuronalcell injury between control rats and rats that received 3 min of hypotension oneday after insult. Quantification of Nissl positive neuronal cells showed asignificant decrease in the number hippocampal cells at day 14. No changes infrontal cortical cells were evident at any time, no significative changes inneurological assessments as well. Our observations show that brief periods ofhemorrhage-induced hypotension actually result in neuronal cell damage inSprague–Dawley rats even if the extent of neuronal damage that wasincurred was not significant enough to cause changes in motor or sensorybehavior.

Erythropoietin acutely decreases airway resistance in the rat

While some experimental data suggest that erythropoietin (EPO) influences respiratory mechanics, reports on scientific trials are lacking. In the present work, respiratory mechanics were measured using the end-inflation occlusion method in control and EPO treated anaesthetised and positive-pressure ventilated rats. Causing an abrupt inspiratory flow arrest, the end-inflation occlusion method makes it possible to measure the ohmic airway resistance and the respiratory system elastance. It was found that EPO induces a significant decrement in the ohmic airway resistance, not noted in control animals, 20 and 30 min after intraperitoneal EPO injection. The elastic characteristics of the respiratory system did not vary. Hypotheses about the mechanism (s) explaining these results were addressed. In particular, additional experiments have indicated that the decrement in airway resistance could be related to an increase in nitric oxide production induced by EPO. Spontaneous increments in plasmatic erythropoietin levels, such as those that take place in association with hypoxia and/or blood loss, appear to be related to the decrement in airway resistance, allowing pulmonary ventilation to increase without altering respiratory mechanics leading to deleterious increments in energy dissipation during breathing.

Repetitive intraperitoneal caspase-3 inhibitor and anesthesia reduces neuronal damage.

Caspase inhibitors are usually administered intracranially. There’s very limited evidence showing that they can be used intraperitoneally, and still have a beneficial effect. We tested the hypothesis that, during focal cerebral ischemia, caspase inhibitors when used in combination with an anesthetic agent results in a significantly reduction in the neuronal damage. Male Sprague Dawley rats were randomly divided into six different groups: control, Isoflurane, Propofol, Isoflurane and Caspase-3 inhibitor intraperitoneally (IP), propofol and Caspase-3 inhibitor IP and only caspase-3 inhibitor, during post-ischemia. Neurological evaluation and histochemical analysis was assessed post-ischemia. The treatment proposed, resulted in a significant decrease in the cerebral infarction volume. Combination of treatments, and caspase-3 inhibitor alone significantly decreased the number of TUNEL and cleaved caspase-3 positive cells in the boundary area of cortical infarction. IP administration appears to reach cerebral targets similarly to intracerebral model. This combination reduces the neurological damage caused by focal cerebral ischemia.

Daily variations of spirometric indexes and maximum expiratory pressure in young healthy adults.

In order to document possible variations in the main spirometric indexes in young healthy adults due to the time of the day, we performed standard and complete spirometric measurements at three different hours of the same day (8 am, 4 pm and 12 am) in 33 healthy, non-smoking young volunteers of both sexes. An index of airway resistance was also calculated. We confirm a general worsening of spirometric indexes at night-time compared to daily hours. This result also includes the main effort-independent indexes which were not previously measured. Maximum expiratory pressure does not show daily variations, while an index of respiratory system resistance exhibits a progressive increase from morning to night.