Ketogenic Diet and Weight Loss: Is There an Effect on Energy Expenditure?

A dysregulation between energy intake (EI) and energy expenditure (EE), the two components of the energy balance equation, is one of the mechanisms responsible for the development of obesity. Conservation of energy equilibrium is deemed a dynamic process and alterations of one component (energy intake or energy expenditure) lead to biological and/or behavioral compensatory changes in the counterpart. The interplay between energy demand and caloric intake appears designed to guarantee an adequate fuel supply in variable life contexts. In the past decades, researchers focused their attention on finding efficient strategies to fight the obesity pandemic. The ketogenic or "keto" diet (KD) gained substantial consideration as a potential weight-loss strategy, whereby the concentration of blood ketones (acetoacetate, 3-beta-hydroxybutyrate, and acetone) increases as a result of increased fatty acid breakdown and the activity of ketogenic enzymes. It has been hypothesized that during the first phase of KDs when glucose utilization is still prevalent, an increase in EE may occur, due to increased hepatic oxygen consumption for gluconeogenesis and for triglyceride-fatty acid recycling. Later, a decrease in 24-h EE may ensue due to the slowing of gluconeogenesis and increase in fatty acid oxidation, with a reduction of the respiratory quotient and possibly the direct action of additional hormonal signals

Sensitivity Analysis of Whole-Room Indirect Calorimeters at the Steady-state Condition

Whole-Room Indirect Calorimeters (WRIC) are accurate tools to precisely measure energy metabolism in humans via calculation of oxygen consumption and carbon dioxide production. Yet, overall accuracy of metabolic measurements relies on the validity of the dynamic model for gas exchange inside the calorimeter volume in addition to experimental and environmental conditions that contribute to the uncertainty of WRIC outcome variables. The aim of this work is to formally study the sensitivity of a WRIC system operated in a push configuration at the steady-state condition to identify the optimal experimental conditions to obtain the best degree of accuracy for outcome metabolic measurements. The results of our sensitivity analysis are then validated with measurements obtained during propane combustion tests performed at the WRIC located at the University Hospital of Pisa. Our results demonstrate that achieving a fractional concentration of carbon dioxide inside the calorimeter >0.2% leads to relative uncertainty <5% for the outcome metabolic measurements when assuming an accuracy class of 1% for gas analyzer instruments

Static sensitivity of whole-room indirect calorimeters

Whole-room indirect calorimeters (WRIC) are accurate tools to precisely measure energy metabolism in humans via calculation of oxygen consumption and carbon dioxide production. Yet, overall accuracy of metabolic measurements relies on the validity of the theoretical model for gas exchange inside the WRIC volume in addition to experimental and environmental conditions that contribute to the uncertainty of WRIC outcome variables. The aim of this study was to quantitatively study the static sensitivity of a WRIC operated in a push configuration and located at the laboratories of the University Hospital of Pisa with the goal to identify the experimental conditions required to reach the best degree of accuracy for outcome metabolic measurements. Herein we demonstrate that achieving a fractional concentration of carbon dioxide inside the WRIC>0.2% at the steady state conditions allows to obtain a relative uncertainty <5% for the outcome metabolic measurement

AUTOPSY STUDY OF TESTICLES IN COVID-19: UPREGULATION OF IMMUNE-RELATED GENES AND DOWNREGULATION OF TESTIS-SPECIFIC GENES

Context Infection by SARS-CoV-2 may be associated with testicular dysfunction that could affect male fertility. Objective Testicles of fatal COVID-19 cases were investigated to detect virus in tissue and to evaluate histopathological and transcriptomic changes. Methods Three groups were compared: (a) uninfected controls (subjects dying of trauma or sudden cardiac death; n = 10); (b) subjects dying of COVID-19 (virus-negative in testes; n = 15); (c) subjects dying of COVID-19 (virus-positive in testes; n = 9). SARS-CoV-2 genome and nucleocapsid antigen were probed using RT-PCR, in situ hybridization, and immunohistochemistry (IHC). Infiltrating leukocytes were typed by IHC. mRNA transcripts of immune-related and testis-specific genes were quantified using the nCounter method. Results SARS-CoV-2 was detected in testis tissue of 9/24 (37%) COVID-19 cases accompanied by scattered T-cell and macrophage infiltrates. Size of testicles and counts of spermatogenic cells were not significantly different among groups. Analysis of mRNA transcripts showed that in virus-positive testes immune processes were activated (interferon-alpha and -gamma pathways). By contrast, transcription of 12 testis-specific genes was downregulated, independently of virus positivity in tissue. By IHC, expression of the luteinizing hormone/choriogonadotropin receptor was enhanced in virus-positive compared to virus-negative testicles, while expression of receptors for androgens and the follicle-stimulating hormone were not significantly different among groups. Conclusion In lethal COVID-19 cases, infection of testicular cells is not uncommon. Viral infection associates with activation of interferon pathways and downregulation of testis-specific genes involved in spermatogenesis. Due to the exceedingly high numbers of infected people in the pandemic, the impact of virus on fertility should be further investigated

The impact of 24 hours fasting and five different overfeeding diets on leptin concentrations in relation to energy expenditure and body weight change in humans

Circulating levels of leptin may play a role in the central regulation of energy expenditure (EE) and maintenance of body weight. Acute negative changes in energy balance such as 24 hours of fasting induce decreases in both leptin levels and EE. On the other hand, positive changes during overfeeding dietary different interventions cause increases in leptin levels and EE. In our recent studies, a greater decrease in EE during fasting predicted less weight loss under caloric restriction and weight gain in free-living conditions. The physiologic underpinnings of the changes in EE are not known but, as leptin changes also with negative or positive energy balance, it is a good candidate for mediating decrease in EE and influencing future weight gain. Fifty-nine healthy subjects (48 men, age: 37±10 y, body fat by DXA: 28±10%) with normal glucose regulation were admitted to our clinical research unit to measure 24h-EE and RQ within a whole room indirect calorimeter during a standard diet in energy balance (EB), 24h fasting (FST) and five different overfeeding diets. Leptin plasma concentrations were measured in the morning prior to and after FST and five different dietary interventions. The percentage change in 24h-EE (%EE) was calculated as the difference divided by the 24h-EE during EB. Follow-up data of weight change were available for 45 subjects after 6 months. As compared to EB, %EE decreased during FST (−7.3±4.4%, p 0.24). Furthermore, percent reduction in leptin during FST did not predict weight change at 6 months (p=0.77) and no correlation were observed between the change in body weight and the leptin change (%) during the five overfeeding diets (all p value > 0.3) Although leptin and EE both decrease during fasting and both increase during overfeeding, the reduction/increase in leptin levels was not associated with the concomitant decline/raise in EE or with subsequent weight change. These results indicate that leptin may not play a major role in the metabolic adaptation to caloric restriction and overfeeding that influences body weight change or at least is a ‘complementary’ hormone, with others appetite hormones, to mediate that process

Underfeeding and oral vancomycin perturb the human gut microbiome and impair nutrient absorption

Studies in mice and humans have indicated that the trillions of microorganisms within the gastrointestinal tract (the gut microbiome) may impact nutrient absorption but direct evidence in humans is lacking. To address this knowledge gap, we conducted a two-phase extended inpatient study in which we directly measured stool calorie loss, a reflection of absorbed nutrients, during dietary (under versus overfeeding) and pharmacologic (oral vancomycin versus placebo) interventions intended to alter the gut microbiome. Food and stool calories were measured by bomb calorimetry. Percent calorie loss was calculated (stool calories/ingested calories) x100. Both interventions (underfeeding and vancomycin treatment) led to greater percent stool calorie loss (indicating decreased nutrient absorption) accompanied by an expansion of Akkermansia muciniphila. Vancomycin also induced further widespread alterations in the gut microbiome structure decreasing gut microbial diversity and changing the relative abundance of all major phyla. The magnitude of the difference in percent calorie loss was similar in the two interventions and both were accompanied by decreased circulating concentrations of butyrate, a short-chain fatty acid which is one of the major end products of microbial metabolism representing a reduction in the availability or processing of nutrients. Interventions that alter energy availability to the gut microbiome either via calorie reduction or by widespread alteration of the microbiome structure increase stool energy loss indicating role for the normal human gut microbiome in the efficiency of nutrient harvest

Aspetti clinici e molecolari della lipodistrofia congenita generalizzata: descrizione di una paziente con sindrome di Berardinelli-Seip dovuta a mutazione del gene AGPAT2.

Le sindromi congenite lipodistrofiche sono caratterizzate da un’anomalia di sviluppo del tessuto adiposo e vengono associate ad accumulo di grasso in sedi ectopiche. Questa difettosa distribuzione dell’adipe corporeo comporta lo sviluppo di alterazioni del metabolismo glucidico e lipidico. La lipodistrofia congenita generalizzata, nota anche come sindrome di Berardinelli Seip (BSCL), è dovuta a mutazioni nei geni AGPAT2 e BSCL2, entrambi fondamentali nel processo di differenziamento adipocitario. In questa tesi viene presentato il caso di una paziente italiana di 54 anni che giungeva alla nostra osservazione per diabete mellito di tipo 2 scarsamente controllato con terapia insulinica. Nata da genitori consanguinei(cugini di primo grado), presentava sin dall’infanzia fenotipo acromegaloide, lipoatrofia diffusa e pseudoipertrofia muscolare. Inoltre venivano riscontrate ipercolesterolemia, ipertrigliceridemia ed ipoleptinemia(0,76ng/ml). Al fine di confermare il sospetto clinico di sindrome di Berardinelli-Seip(BSCL) venivano analizzate le sequenze dei geni candidati. Il DNA della paziente era estratto dai leucociti di sangue periferico ed amplificato mediante PCR. Dallo screening genetico non e’ risultata alcuna mutazione nella sequenza del gene BSCL2, mentre veniva ritrovata una nuova variante in forma omozigote nell’esone 3 del gene AGPAT2, che comporta la sostituzione dell’aminoacido Prolina in posizione 112 con l’amminoacido Leucina (Pro112Leu). I risultati ottenuti dallo screening genetico, associati alle caratteristiche cliniche della paziente, hanno permesso di confermare la diagnosi di Sindrome di Berardinelli-Seip

Effects of tyrosine kinase inhibitors on thyroid function and thyroid hormone metabolism

The increasing knowledge of the molecular mechanisms in the cell signaling pathways of malignant cells, has recently led to the discovery of several tyrosine kinases (TKs), mainly TK receptors (TKR), which play a major role in the pathogenesis of many types of cancer. These receptors, physiologically involved in cell growth and angiogenesis, may harbor mutations or be overexpressed in malignant cells, and represent a target for anticancer therapy. Indeed, several therapeutic agents targeting specific altered pathways such as RET, BRAF, RAS, EGFR and VEGFR, have been identified. Tyrosine kinase inhibitors (TKIs) affect TK dependent oncogenic pathways by competing with ATP binding sites of the TK domain, thus blocking the activity of the enzyme, and thereby inhibiting the growth and spread of several cancers. Although the therapeutic action may be very effective, these molecules, due to their mechanism of multi- targeted inhibition, may produce adverse events involving several biological systems. Both hypothyroidism and thyrotoxicosis have been reported during treatment with TKI, as well as an effect on the activity of enzymes involved in thyroid hormone metabolism. The pathogenic mechanisms leading to thyroid dysfunction and changes in serum thyroid function tests occurring in patients on TKI are reviewed and discussed in this manuscript

Understanding the effect of obesity on papillary thyroid cancer: is there a need for tailored diagnostic and therapeutic management?

Introduction: Several studies have focused on the relationship between obesity and differentiated thyroid carcinoma (DTC), particularly papillary histotype (PTC). However, the association of obesity with both incidence and aggressiveness of PTC is still incompletely understood.Areas covered: We reviewed the mechanisms underlying the cross talk between obesity and thyroid carcinomas and described the most recent evidence evaluating the effect of obesity on the development of PTC, as well as the impact of excessive body weight on the clinicopathologic features and outcome of this type of cancer.Expert opinion: Available evidence suggests that excessive body weight is linked with a higher risk of getting PTC, while its impact on the aggressiveness of the disease, if present, is still not clear. Therefore, while attention should be paid to discover thyroid cancer in patients with obesity earlier, once diagnosed it should be managed following a conventional workup as in normal weight patients, based on the clinical presentation of the disease and including active surveillance if appropriate, as recommended by referral guidelines

Molecular Genetics of Follicular-Derived Thyroid Cancer

Thyroid cancer is the most common type of endocrine-related malignancy, whose incidence rates have increased dramatically in the last few decades. Neoplasms of follicular origin generally have excellent prognosis, with the exception of less differentiated tumors. Follicular-derived thyroid cancer can manifest as a variety of morphologically distinct entities, characterized by various degrees of differentiation and invasiveness. Histological evaluation is thus crucial for the definition of patients’ prognosis. However, within each histological subtype, tumor behavior can be highly variable, and, in this respect, molecular characterization can provide insightful information to refine the risk stratification of tumors. In addition to the importance of its prognostic role, molecular testing can be used to support the differential diagnosis of thyroid nodules in the absence of marked cyto-morphological aberrations. Finally, with the advent of targeted drugs, the presence of molecular alterations will guide the therapeutic strategies for patients with advanced tumors who do not respond to standard treatment. This review aims to describe the genetic landscape of follicular-derived thyroid tumors also highlighting differences across histological subtypes