Ghrelin, paper review part I

For more: Book Review and Comment

Big glucose model (talk part 1)

See also

The big glucose model: the quest for unification

Food Intake vs. Metabolism: body weight control

In the following diagram, we organize several hormones and molecules (in general peptides) that play a central role in glucose control. The coming text dissert on each of them, and others. The most important to understand is that glucose is the main energy of the body and it must be refuelled from time to time, however this time to time is not always predictable, and how biological system must manage the energy already present until the next meal. Even in the meal time, it is necessary to "take it easy", it must be controlled how much to eat, and as well the absorption of the glucose. It is achieved through a network of interconnected hormones and vital molecules, some in the brain, some in strategic places such as the guts and pancreas. Body weight is a quite important parameter for the body: too much weight means too much energy to keep it, too less energy means not enough power in important situations. 

Schematic viewpoint of the hormones involved in the appetite control and metabolism. In red are important players, but are not hormones. The dashed arrows intend to show hormones that plays more then one control function on the diagram, the challenge is to build a complete diagram on this style, even in layers, that is, one hormone may control others such in gene expression, transcription networks; e.g. some researches show that leptin can control insulin⁽¹¹⁾. This diagram is mathematical modeling biased. The "fat" arrow between body weight and metabolism intends to say that the metabolism is a short-term dynamic process, from seconds to hours. whereas the body weight changes in a long-term scale, from days to months. Source: own elaboration.

See also

The big glucose model: the quest for unification

The big glucose model: the quest for unification

The coupling of hormonal responses to nutrient availability is fundamental for metabolic control⁽¹⁾. Metabolism is the important step in which living systems balance the energy available and the energy demanded, on such a way that the organism will not find itself in a situation of lacking energy after an abundance⁽¹⁾. Independent of scientific advances, our body works, it is a miracle of control system in practice. Glucose is constantly converted to glycogen, "the battery of living systems", constantly it is brought back to the bloodstream. 

Controversy underscores the fact that, despite the impressive progress made over the past few decades in unraveling many of the molecular pathways involved in energy regulation, we still have a rather murky understanding of how all the pieces fit together to function as an integrated system⁽³⁾. For instance, recently a new hormone long ago guessed was finally identified, called neuromedin U⁽¹⁾, firstly screened off in fruit fly, called limostatin. Basically this hormone works when we are fasting, it avoids glucose to be stored in situations in which it supposes to be available.

A literature analysis shows a considerable about of hormones and molecules involved in the complex process of eating and managing energy. Food is equal energy, energy is equal work. We do work from simples tasks such as sleeping to more complex ones and elaborated tasks such as playing out favorite sport game. 

References

1. Alfa RW, Park S, Skelly KR, Poffenberger G, Jain N, Gu X, Kockel L, Wang J, Liu Y, Powers AC, Kim SK. Suppression of insulin production and secretion by a decretin hormone. Cell Metab. 2015 Feb 3;21(2):323-33. doi: 10.1016/j.cmet.2015.01.006.

2. K. N. Frayn. Metabolic Regulation: A Human Perspective. Third Edition. Wiley-blackwell. 2010.

3. J. Tam, Dai Fukumura, and Rakesh K. Jain. A mathematical model of murine metabolic regulation by leptin: energy balance and defense of a stable body weight. Cell Metab. 2009 January 7; 9(1): 52–63. doi:10.1016/j.cmet.2008.11.005.

4. Pasquale Palumbo, Susanne Ditlevsen, Alessandro Bertuzzi, Andrea De Gaetano, Mathematical modeling of the glucose–insulin system: A review, Mathematical Biosciences 244 (2013) 69–81.