Mexican Plants Involved in Glucose Homeostasis and Body Weight Control: Systematic Review.

BACKGROUND: Obesity is defined as abnormal or excessive fat accumulation, provoking many different diseases, such as obesity and type 2 diabetes. Type 2 diabetes is a chronic-degenerative disease characterized by increased blood glucose levels. Obesity and type 2 diabetes are currently considered public health problems, and their prevalence has increased over the last few years. Because of the high cost involved in the treatment of both diseases, different alternatives have been sought. However, the general population uses medicinal plants, in the form of tea or infusions, to treat different diseases. Therefore, traditional medicine using medicinal plants has been investigated as a possible treatment for type 2 diabetes and body weight control. AIM OF THE STUDY: The purpose of this review is to find medicinal plants used in Mexico that could exert their beneficial effect by regulating insulin secretion and body weight control. MATERIAL AND METHOD: For the development of this review, Mexican plants used in traditional medicine to treat type 2 diabetes and body weight control were searched in PubMed, Google Scholar, and Scopus. The inclusion criteria include plants that presented a significant reduction in blood glucose levels and/or an increase in insulin secretion. RESULTS: We found 306 Mexican plants with hypoglycemic effects. However, plants that did not show evidence of an increase in insulin secretion were eliminated. Finally, only five plants were included in this review: Momordica charantia L. (melón amargo), Cucurbita ficifolia bouché (chilacayote), Coriandrum sativum L. (cilantro), Persea americana Mill. (aguacate) Bidens pilosa (amor seco), including 39 articles in total. Here, we summarized the plant extracts (aqueous and organic) that have previously been reported to present hypoglycemic effects, body weight control, increased secretion and sensitivity of insulin, improvement of pancreatic ß cells, and glucose tolerance. Additionally, these effects may be due to different bioactive compounds present in the plants' extracts. CONCLUSION: Both in vivo and in vitro studies are required to understand the mechanism of action of these plant extracts regarding insulin secretion to be used as a possible treatment for type 2 diabetes and body weight control in the future.

The Role of the Novel Lipokine Palmitoleic Acid in Health and Disease.

The monounsaturated fatty acid palmitoleate (palmitoleic acid) is one of the most abundant fatty acids in serum and tissues, particularly adipose tissue and liver. Its endogenous production by stearoyl-CoA desaturase 1 gives rise to its cis isoform, cis-palmitoleate. Although trans-palmitoleate is also synthesized in humans, it is mainly found as an exogenous source in ruminant fat and dairy products. Recently, palmitoleate was considered to be a lipokine based on evidence demonstrating its release from adipose tissue and its metabolic effects on distant organs. After this finding, research has been performed to determine whether palmitoleate has beneficial effects on metabolism and to elucidate the underlying mechanisms. Thus, the aim of this work was to review the current status of knowledge about palmitoleate, its metabolism, and its influence on metabolic abnormalities. Results have shown mixed cardiovascular effects, direct or inverse correlations with obesity, and hepatosteatosis, but a significant amelioration or prevention of insulin resistance and diabetes. Finally, the induction of palmitoleate release from adipose tissue, dietary intake, and its supplementation are all interventions with a potential impact on certain metabolic diseases.

Hypothalamic Vitamin D Improves Glucose Homeostasis and Reduces Weight.

Despite clear associations between vitamin D deficiency and obesity and/or type 2 diabetes, a causal relationship is not established. Vitamin D receptors (VDRs) are found within multiple tissues, including the brain. Given the importance of the brain in controlling both glucose levels and body weight, we hypothesized that activation of central VDR links vitamin D to the regulation of glucose and energy homeostasis. Indeed, we found that small doses of active vitamin D, 1α,25-dihydroxyvitamin D3 (1,25D3) (calcitriol), into the third ventricle of the brain improved glucose tolerance and markedly increased hepatic insulin sensitivity, an effect that is dependent upon VDR within the paraventricular nucleus of the hypothalamus. In addition, chronic central administration of 1,25D3 dramatically decreased body weight by lowering food intake in obese rodents. Our data indicate that 1,25D3-mediated changes in food intake occur through action within the arcuate nucleus. We found that VDR colocalized with and activated key appetite-regulating neurons in the arcuate, namely proopiomelanocortin neurons. Together, these findings define a novel pathway for vitamin D regulation of metabolism with unique and divergent roles for central nervous system VDR signaling. Specifically, our data suggest that vitamin D regulates glucose homeostasis via the paraventricular nuclei and energy homeostasis via the arcuate nuclei.

Expression of new loci associated with obesity in diet-induced obese rats: from genetics to physiology.

Genome-wide association studies (GWAS) are a powerful tool for revealing genes associated with common human obesity. New loci associated with obesity have recently been reported, but their function and metabolic implications remain to be elucidated. In order to begin identifying the role of some of these obesity-related loci, the closest genes to the polymorphism of each locus were selected and their expression was compared in the hypothalamus, adipose tissue, liver, soleus muscle, and extensor digitorum longus muscle (EDL) of Long-Evans rats maintained on chow or a high-fat diet (HFD) for 6 weeks. From a total of 19 genes analyzed, seven genes (ETV5, FTO, GNPDA2, KCTD15, TMEM18, MC4R, and SH2B1) were down-regulated in the hypothalamus of HFD compared to chow-fed rats. In adipose tissue of rats fed on HFD, the mRNA levels of BCDIN3, KCTD15, and SULT1A1 were down-regulated, whereas those of MTCH2, PTER, and TUFM were up-regulated. In the liver, three genes were up-regulated (PTER, SULT1A1, and TUFM) in HFD relative to chow-fed rats, and TMEM18 was down-regulated. Finally, in soleus muscle of HFD-fed rats, BCDIN3, BDNF, and TMEM18 were down-regulated, and in the EDL muscle SH2B1 and TUFM were up-regulated. mRNA levels in the hypothalamus were compared between fed and fasted states, and only KCTD15 was down-regulated during fasting when fed a chow diet. In conclusion, novel genes found to be associated with obesity are regulated by a HFD and the mRNA levels of KCTD15 is dependent on the nutritional status. These results suggest a potential role of these genes in the regulation of energy balance.