In all vertebrates, food intake is a sophisticated complexof neurohumoral networks that convey signals between thebrain and periphery, to modulate energy status. Gut hor-mones, such as peptide YY, pancreatic polypeptide, glucagon-like peptide-1, oxyntomodulin, and ghrelin, are modulatedby acute food ingestion. In contrast, adiposity signals suchas leptin and insulin are implicated in both short- and long-term energy homeostases.Themechanisms of action of thesesubstances are similar among vertebrates.
Their regulation might vary with the feeding and repro-ductive state, and between different tissues and organs, andit might also be affected by environmental parameters. Thecontrol of food intake is carried out by short-term andlong-term regulation mechanisms. The short-term signalsact primarily as determinants of satiety to limit the sizeof individual meals. Long-term signals communicate totalenergy stores, integrate over time, and interact with othersystems that rely upon the energy status of the organism (e.g.,growth, immune function, and reproduction). Both long-and short-term signals interact to influence the behavior andenergy balance of the organism. We know that disruptedsignaling in many of these systems leads to dramatic changesin feeding behavior and weight gain (or loss). However, fullyunderstanding control of food intake will require knowledgeof: (a) which peptides are involved; (b) areas of the centralnervous system where this peptides are expressed and (c)assessment of the biological effects of the different neu-ropeptides in the integrated control of energy and metabolichomeostasis.
In this special issue we selected several papers that carryout a systematic and critical review of some of the topics that
following recent developments are currently at the forefrontof obesity research. This special issue is particularly timelysince it becomes available 20 years after the seminal discoveryof leptin in Friedman’s lab.
H. M. Zeron et al. provide a deep and comprehensivereview of the different gut hormones involved in energyhomeostasis; they give an update on the available evidenceregarding the interaction between macronutrients and gas-trointestinal hormone secretion. Furthermore, they reviewthe available data regarding the evidences postulating a yetuncharacterized production of a putative hormone producedin the foregut of diabetic patients that should act decreasinginsulin-sensitivity at peripheral tissues. This topic is of par-ticular clinical relevance since it provides a rationale for theso-called metabolic surgery that has been advocated by someas possible therapy in diabetic patients.
Most of the data gleaned over the last 20 years inenergy homeostasis has been focused in the integratedcontrol exerted at hypothalamic level between central andperipheral signals. The latter arises from the gastrointestinaltract, including the pancreas, and the adipose tissue. Morerecently it has become evident that proteins secreted for otherperipheral tissues may also play an important role. Thus anew set of factors so-called myokines, produced by muscleand released into the blood circulation, has emerged as majorregulators of energy and metabolic homeostasis. A recentlydiscovered one, irsin, is postulated as a potential drug targetdue to its marked effects on energy expenditure and thereforebody weight. The available data in this topic is reviewed byM. G. Novelle et al., who provide a critical assessment atthe available evidences so far and some of the yet remaining
Hindawi Publishing CorporationInternational Journal of EndocrinologyVolume 2014, Article ID 910912, 2 pageshttp://dx.doi.org/10.1155/2014/910912
2 International Journal of Endocrinology
questions regarding the mechanisms involved in its secretionand biological effects.
The intimate relationship between energy status andreproduction has been recognized for many years. Datagleaned more recently have clearly shown that signals, suchas leptin and ghrelin, known to be involved in the regulationof energy homeostasis do also play an important role in thecontrol of the hypothalamus-pituitary-gonadal axis. How-ever, themechanisms involved at central levelmediating theireffects have only recently become clearer. In this special issue,J. Roa provides an overview of the most recent developmentsin the field. In particular, a deepmechanistic insight assessingthe implication of GnRH, Kiss1, NPY, and POMC neurons asthe key factors contributing to the adaptation of the gonadalaxis to different metabolic status is put forward.
Anorexia and bulimia nervosa are two clinical entitiescharacterized by abnormal eating behavior. Despite manyyears of research, themechanisms involved are far from beingclarified. K. Smitka et al. extensively review the involvementof the different neuronal networks implicated in food intakeand the available evidences regarding the alteration of differ-ent hormones and neuropeptides as potential physiopatho-logical mechanisms in these two diseases. Furthermore theycarry out a thorough assessment of the potential involvementof neutralizing autoantibodies against these peptides.
A topic that was neglected for many years but that isnow at the forefront of research is the assessment of nutritionand anxiety. M. Murphy and J. G. Mercer review the mostrecent developments in the field. In particular, they criticallyreview available data on the influence of different dietarycomponents on anxiety-like behavior. Furthermore, theyhighlight the importance of fetal and neonatal programmingand the limitations when comparing the outcomes of trialsthat involve differences in diet, species, strain, sex, and lifestage, coupled with variation in duration, environment, andoutcome measure.
Most of the studies regarding body weight homeostasiswere focused in the issue of energy intake. Over the lastfew years considerable attention has been given to the studyof mechanisms that promote or are stimulated by palatablefood. J. R. Barson et al. addressed this issue by focusingon the two neuropeptides historically related to the lateralhypothalamus. They provide us with a deep insight into themechanisms by which orexin and MCH promote the intakeof palatable and/or caloric food and how the intake of thesefoods can influence the activity of the neurons producingthese neuropeptides. In addition they describe their effects onthe different brain area implicated in food reward. ¡ack¿¡title/¿
Acknowledgment
The guest editors wish to thank all authors for their valuablecontributions. Without their efforts, this special issue wouldnot have been possible.
