LKB1 up-regulation inhibits hypothalamic inflammation and attenuates diet-induced obesity in mice.

BACKGROUND: Diet-induced obesity (DIO) is associated with chronic, low-grade inflammation in the hypothalamus. The inflammatory pathway of the hypothalamus is activated during obesity, and inhibition of activation of the inflammatory pathway can partially reverse obesity. Therefore, exploring new targets for inhibiting hypothalamic inflammation will provide new ideas for the prevention and treatment of obesity. Liver kinase B1 (LKB1), a serine/threonine kinase, is a tumor suppressor and metabolic regulator. Recent studies have shown that LKB1 has a certain anti-inflammatory effect. However, a role of LKB1 in the regulation of hypothalamic inflammation remains unclear. Therefore, we examined whether LKB1 overexpression in the hypothalamus could weaken the hypothalamic inflammation and inhibit the development of obesity. METHODS: LKB1 overexpressing adeno-associated virus (AAV) particles were injected stereotactically into the third ventricle (3 V) of C57BL/6 mice fed with HFD. We assessed changes in body mass and adiposity, food intake, hypothalamic inflammatory markers, and energy and glucose metabolism. RESULTS: LKB1 up-regulation in hypothalamus attenuated diet-induced hypothalamic inflammation, reduced food intake and body weight gain. In addition, the overexpression of hypothalamic LKB1 increased the insulin sensitivity and improved whole-body lipid metabolism, which attenuated hepatic fat accumulation and serum lipid levels. CONCLUSION: Hypothalamic LKB1 up-regulation attenuates hypothalamic inflammation, and protects against hypothalamic inflammation induced damage to melanocortin system, resulting in lower food intake and lower fat mass accumulation, which consequently protects mice from the development of obesity. Our data suggest LKB1 as a novel negative regulator of hypothalamic inflammation, and also a potentially important target for treating other inflammatory diseases.

Deletion of liver kinase B1 in POMC neurons predisposes to diet-induced obesity.

AIMS: Liver kinase B1 (LKB1) is a serine/threonine kinase. Although many biological functions of LKB1 have been identified, the role of hypothalamic LKB1 in the regulation of central energy metabolism and susceptibility to obesity is unknown. Therefore, we constructed POMC neuron-specific LKB1 knockout mice (PomcLkb1 KO) and studied it at the physiological, morphological, and molecular biology levels. MAIN METHODS: Eight-week-old male PomcLkb1 KO mice and their littermates were fed a standard chow fat diet (CFD) or a high-fat diet (HFD) for 3 months. Body weight and food intake were monitored. Dual-energy X-ray absorptiometry was used to measure the fat mass and lean mass. Glucose and insulin tolerance tests and serum biochemical markers were evaluated in the experimental mice. In addition, the levels of peripheral lipogenesis genes and central energy metabolism were measured. KEY FINDINGS: PomcLkb1 KO mice did not exhibit impairments under normal physiological conditions. After HFD intervention, the metabolic phenotype of the PomcLkb1 KO mice changed, manifesting as increased food intake and an enhanced obesity phenotype. More seriously, PomcLkb1 KO mice showed increased leptin resistance, worsened hypothalamic inflammation and reduced POMC neuronal expression. SIGNIFICANCE: We provide evidence that LKB1 in POMC neurons plays a significant role in regulating energy homeostasis. LKB1 in POMC neurons emerges as a target for therapeutic intervention against HFD-induced obesity and metabolic diseases.

Diet-induced obese rats exhibit impaired LKB1-AMPK signaling in hypothalamus and adipose tissue.

AMPK not only acts as a sensor of cellular energy status but also plays a critical role in the energy balance of the body. In this study, LKB1-AMPK signaling was investigated in diet-induced obese (DIO) and diet resistant (DR) rats. In hypothalamus, DIO rats had lower level of LKB1, AMPKα and pAMPKα than chow-fed or DR rats. Both orexigenic peptide NPY and anorexigenic peptide POMC expression were reduced in hypothalamus of DIO rats. i.c.v. injection of AICAR, an activator of AMPK, increased NPY expression but did not alter POMC expression in DIO rats. In periphery, LKB1 protein content and pAMPKα level were lower in the adipose tissue of DIO rats compared to chow-fed and DR rats. Moreover, pAMPKα and LKB1 protein levels obtained from epididymal fat pad were inversely correlated with epididymal fat mass. LKB1 protein content and pAMPKα in skeletal muscle of DIO rats were not different from those in the muscles of chow-fed and DR rats. In summary, DIO rats, but not DR rats, have impaired LKB1-AMPK signaling in hypothalamus and adipose tissue, suggesting the disturbed energy balance observed in DIO rats is related with abnormalities of AMPK signaling in a tissue specific manner.

Proteomic analysis of rat hypothalamus revealed the role of ubiquitin-proteasome system in the genesis of DR or DIO.

Obesity has become a global epidemic, contributing to the increasing burdens of cardiovascular disease and type 2 diabetes. However, the precise molecular mechanisms of obesity remain poorly elucidated. The hypothalamus plays a major part in regulating energy homeostasis by integrating all kinds of nutritional signals. This study investigated the hypothalamus protein profile in diet-induced obese (DIO) and diet-resistant (DR) rats using two dimensional gel electrophoresis (2-DE) combined with MALDI-TOF/TOF-MS analysis. Twenty-two proteins were identified in the hypothalamus of DIO or DR rats. These include metabolic enzymes, antioxidant proteins, proteasome related proteins, and signaling proteins, some of which are related to AMP-activated protein kinase (AMPK) signaling or mitochondrial respiration. Among these proteins, in comparison with the normal-diet group, Ubiquitin was significantly decreased in DR rats but not changed in DIO rats, while Ubiquitin carboxyl-terminal esterase L1 (UCHL-1) was decreased in DIO rats but not changed in DR rats. The expression level of Ubiquitin and UCHL-1 were further validated using Western blot analysis. Our study reveals that Ubiquitin and UCHL-1 are obesity-related factors in the hypothalamus that may play an important role in the genesis of DR or DIO by interfering with the integrated signaling network that control energy balance and feeding.

Peroxiredoxin1: a potential obesity-related factor in the hypothalamus.

BACKGROUND: Obesity has become a global epidemic and contributes to the increasing burden of type 2 diabetes, cardiovascular disease and some cancers worldwide. However, the precise molecular mechanisms of obesity remain poorly elucidated. Recent data indicate monitoring of brain energy status especially in the hypothalamus, is crucial for energy homeostasis. Anti-oxidant defenses are suggested to play an important role in production of a well-balanced signal, which is necessary for adjusted neuronal activities. MATERIAL/METHODS: Hypothalamus proteomes of the diet-induced obesity (DIO) and diet-resistant (DR) rats were analyzed using 2-dimensional gel electrophoresis (2-DE) combined with MALDI-TOF/TOF-MS analysis. RESULTS: The 2-DE maps showed a resolution of 1280±15, 1250±10, 1260±12 protein spots in normal, DIO and DR groups, respectively. Twenty-two proteins were identified in the hypothalamus of DIO or DR rats. These proteins are involved in metabolism enzymes, antioxidant proteins, proteasome-related proteins and signaling proteins. In comparison with normal-diet group, peroxiredoxin1 (Prx1) was significantly decreased in DR group and it was increased in DIO group. The expression of Prx1 was further validated by Western blot analysis. CONCLUSIONS: The differential expression of Prx1 in DR and DIO groups indicated that the antioxidant protein may play an important role in the genesis of DR or DIO. This study provides new clues to illuminate the mechanisms involved in the progress of DIO and DR in the hypothalamus.

Electroacupuncture in the treatment of obesity.

Obesity is becoming one of the most common health problems in the world. Many other disorders, such as hypertension and diabetes are considered as the consequences of obesity. Since effective remedies are rare (only two drugs, Orlistat and Sibutramine, were officially approved by the US Food and Drug Administration for long-term obesity treatment so far), researchers are trying to discover new therapies for obesity, and acupuncture is among the most popular alternative approaches. To facilitate weight reduction, one can use manual acupuncture, electroacupuncture (EA) or transcutaneous electrical acupoint stimulation (TEAS). As the parameters of the EA or TEAS can be precisely characterized and the results are more or less reproducible, this review will focus on EA as a treatment modality for obesity. Results obtained in this laboratory in recent five years will be summarized in some detail.

Electroacupuncture suppresses expression of gastric ghrelin and hypothalamic NPY in chronic food restricted rats.

Electroacupuncture (EA) has been reported to reduce body weight in overweight subjects in clinical practice, as well as in rats and mice with diet-induced obesity. In the present study, this effect of EA was tested in lean rats subjected to long-term food restriction (FR, food was offered only 1 h/day). Two hertz EA administered once every other day produced a further reduction in body weight in FR rats. Exploration of the mechanism involved revealed significant downregulation of the orexigenic peptides: ghrelin in the stomach, and neuropeptide Y (NPY) but not Agouti-related peptide (AgRP) in the hypothalamus, which was in line with the reduction in food intake in rats receiving EA stimulation as compared with those receiving restraint only. Uncoupling protein 3 (UCP3), involved in accelerating energy expenditure, was not significantly altered. These results suggest that the EA-induced body weight reduction was due mainly to a decrease in food intake rather than an increase in energy expenditure. A reduction in the orexigenic peptides ghrelin and NPY may be involved in the underlying mechanism.

Distribution of beacon immunoreactivity in the rat brain.

Beacon is a novel peptide isolated from the hypothalamus of Israeli sand rat. In the present study, we determined the distribution of beacon in the rat brain using immunohistochemical approach with a polyclonal antiserum directed against the synthetic C-terminal peptide fragment (47-73). The hypothalamus represented the major site of beacon-immunoreactive (IR) cell bodies that were concentrated in the paraventricular nucleus (PVN) and the supraoptic nucleus (SON). Additional immunostained cells were found in the septum, bed nucleus of the stria terminalis, subfornical organ and subcommissural organ. Beacon-IR fibers were seen with high density in the internal layer of the median eminence and low to moderate density in the external layer. Significant beacon-IR fibers were also seen in the nucleus of the solitary tract and lateral reticular formation. The beacon neurons found in the PVN were further characterized by double label immunohistochemistry. Several beacon-IR neurons that resided in the medial PVN were shown to coexpress corticotrophin-releasing hormone (CRH) and most labeled beacon fibers in the external layer of median eminence coexist with CRH. The topographical distribution of beacon-IR in the brain suggests multiple biological activities for beacon in addition to its proposed roles in modulating feeding behaviors and pituitary hormone release.

Up-regulation of the expression of cocaine and amphetamine-regulated transcript peptide by electroacupuncture in the arcuate nucleus of diet-induced obese rats.

It was reported that acupuncture or electro-acupuncture (EA) is effective in reducing the body weight for obese patients, although the mechanisms remain obscure. In a previous study, we have found that rats fed with high-fat (HIF) diet developed diet-induced obesity (DIO) with a concomitant decrease in the hypothalamic content of the cocaine and amphetamine-regulated transcript (CART) peptide, a peptide with anorexiogenic effect. To assess the central effect of EA on DIO rat, we revealed that EA up-regulated the expression of CART peptide in the arcuate nucleus (ARC) of the DIO rats. After feeding with HIF diet for 14 weeks, the DIO rats received EA stimulation three times per week for 4 weeks. The expression of CART peptide in ARC was measured using immunohistochemistry. The plasma ACTH was measured with ELISA. EA caused a reduction of both body weight and energy intake in DIO rats and increased the expression of CART peptide in ARC. The plasma ACTH was increased in response to restraint stress, but EA produced no further increase in ACTH levels. The results suggest that EA can up-regulate the expression of CART peptide to approach normal level, resulting in an inhibition of food intake and a reduction of body weight in DIO rats.

[Electroacupuncture up-regulated arcuate nucleus alpha-MSH expression in the rat of diet-induced obesity].

OBJECTIVE: To investigate the effect of electroacupuncture (EA) on rat with diet-induced obesity (DIO) and to explore the possible neurochemical mechanisms using the technique of immumohistochemistry. METHODS: To establish DIO rat model by feeding the animals with high fat diet for 14 weeks. DIO rats were randomly divided into 4 groups: (1) 2Hz EA group, (2) 100Hz EA group, (3) restrain control group, (4) diet resistance (DR) group, (5) DIO group and (6) normal control group. EA treatment: (1) The acupoints used were Zusanli and Sanyinjiao on both legs. (2) The intensities of stimulation were 0.5, 1.0 and 1.5mA for 10 mins each. EA treatment was administered 3 times per week. Food intake and body weight were measured daily for 4 weeks. (3) The changes of the expression of alpha-melanocyte-stimulating hormone (alpha-MSH) in the hypothalamic arcuate nucleus (ARC) were measured with immunohistochemical semiquantitative analysis. RESULTS: (1) The food intake and body weight of 2 Hz EA group and 100 Hz EA group were decreased significantly compared with the restrain control group and DIO group. (2) The number of alpha-MSH positive cells in hypothalamic ARC in 2 Hz EA and 100 Hz EA group was significantly higher than that in restrain control group and DIO group. The number of alpha-MSH positive cells in hypothalamic ARC in DIO group is significantly lower than those in DR group or normal control group. CONCLUSION: A decrease of alpha-MSH level in hypothalamus may be associated with diet-induced obesity. The therapeutic effect on obesity produced by EA may be accounted for by the stimulation of pro-opio-melanocortin neurons in hypothalamic ARC to release alpha-MSH, which inhibits food intake, resulting in a decrease of body weight.

[Study on the effect of transcutaneous electric nerve stimulation on obesity].

OBJECTIVE: To evaluate the effect of transcutaneous electrical stimulation produced by Han's acupiont nerve stimulator (HANS) in treating obesity. METHODS: Sixteen volunteers with primary obesity were recruited, without any instructions or attempts to control their dietary. The trial started in November 2001 and ended in June 2002. Each obese volunteer received transcutaneous electric nerve stimulation (TENS) at 8 acupoints. The electrical parameters were: frequency at 2 Hz, with pulses width of 0.6 ms; intensity varied depending on individual's sensitivity to electrical stimulation to maintain a comfortable level. The treatment was administered 3 times per week. Body weight was recorded before each TENS treatment. RESULTS: The main value of body weight decreased gradually during the trial, with a net decrease of (2.06 +/- 0.31) kg at the end of 12 weeks' treatment (the first phase), corresponding to a decrease of (2.78 +/- 0.40)% as compared with the initial body weight (P < 0.01). In the interim period of 4 weeks (during the Chinese Spring Festival), a partial recurrence of the body weight occurred. During the second phase of treatment lasting for 15 weeks, there was again a reduction of body weight for (2.81 +/- 0.68) kg, corresponding to a decrease of (3.90 +/- 0.40)% (P < 0.001) as compared with the pretreatment level. CONCLUSION: An open trial of HANS treatment revealed a moderate, but significant effectiveness on weight reduction in a group of people with primary obesity. The therapy remains effective for the second phase of treatment. It is anticipated that a better effect can be achieved if the treatment is accompanied with diet control and appropriate exercise.