Identification of the principal transcriptional regulators for low-fat and high-fat meal responsive genes in small intestine.

BACKGROUND: High-fat (HF) diet is a well-known cause of obesity. To identify principle transcriptional regulators that could be therapeutic targets of obesity, we investigated transcriptomic modulation in the duodenal mucosa following low-fat (LF) and HF meal ingestion. METHODS: Whereas one group of mice was sacrificed after fasting, the others were fed ad libitum with LF or HF meal, and sacrificed 30 min, 1 h and 3 h after the beginning of the meal. A transcriptome analysis of the duodenal mucosa of the 7 groups was conducted using both microarray and serial analysis of gene expression (SAGE) method followed by an Ingenuity Pathways Analysis (IPA). RESULTS: SAGE and microarray showed that the modulation of a total of 896 transcripts in the duodenal mucosa after LF and/or HF meal, compared to the fasting condition. The IPA identified lipid metabolism, molecular transport, and small molecule biochemistry as top three molecular and cellular functions for the HF-responsive, HF-specific, HF-delay, and LF-HF different genes. Moreover, the top transcriptional regulator for the HF-responsive and HF-specific genes was peroxisome proliferator-activated receptor alpha (PPARα). On the other hand, the LF-responsive and LF-specific genes were related to carbohydrate metabolism, cellular function and maintenance, and cell death/cellular growth and proliferation, and the top transcriptional regulators were forkhead box protein O1 (FOXO1) and cAMP response element binding protein 1 (CREB1), respectively. CONCLUSIONS: These results will help to understand the molecular mechanisms of intestinal response after LF and HF ingestions, and contribute to identify therapeutic targets for obesity and obesity-related diseases.

Atlas of dihydrotestosterone actions on the transcriptome of prostate in vivo.

BACKGROUND: Using serial analysis of gene expression (SAGE), we studied the transcriptomic changes in vivo by dihydrotestosterone (DHT) treatment in mice to better understand androgen effects in the prostate. METHODS: Approximately 872,000 SAGE tags were isolated from intact and castrated (GDX) mice with and without DHT injection. RESULTS: GDX significantly altered 431 transcripts, including 110 transcripts restored by DHT, and 146 potentially new transcripts. Totally, 187 transcripts were significantly affected by DHT treatment, of which 124 were induced and 63 were repressed. Interestingly and consistent with the prostate's secretory role, DHT up-regulated the expression of many genes involved in various steps of protein metabolism such as synthesis, folding, and secretion. GDX modulated the expression of genes which induce cell apoptosis and inhibit cell proliferation through polyamine biosynthesis, retinoid X receptor actions as well as several signaling pathways and some related factors. These results clarify DHT effects on prostate transcriptome in the areas of protein metabolism, cell proliferation and apoptosis. In addition, we detected gene expression changes in metabolic pathways, cytoskeleton, immunity and endoplasmic reticulum stress. Furthermore, knockdown of S-adenosylmethionine decarboxylase 1 in LNCaP cells confirmed the importance of androgen-regulated genes (ARGs) in prostate cancer cell growth. CONCLUSION: Our data support the idea that ARGs are essential for the normal development of the prostate and can also be responsible for the pathogenesis of the prostate cancer.

Prostate-specific genes and their regulation by dihydrotestosterone.

BACKGROUND: Prostate is a well-known androgen-dependent tissue. METHODS: By sequencing 4,294,186 serial analysis of gene expression (SAGE) tags, we have investigated the transcriptomes of normal mouse prostate, liver, testis, lung, brain, femur, skin, adipose tissue, skeletal muscle, vagina, ovary, mammary gland, and uterus in order to identify the most abundant and tissue-specific transcripts in the prostate, as well as to target the androgen responsive transcripts specifically regulated in the prostate. Small interference RNA (siRNA) in LNCaP cells was applied to validate the roles of prostate-specific/enriched ARGs in the growth of human prostate cancer cells. RESULTS: The most abundant transcripts were involved in prostatic secretion, energy metabolism and immunity. Previously well-known prostate-specific transcripts, including many transcripts involved in prostatic secretion, polyamine biosynthesis and transport, and immunity were specific/enriched in the prostate. Only 22 transcripts among 114 androgen-regulated genes (ARGs) in the mouse prostate were modulated by dihydrotestosterone (DHT) in two or more tissues. The siRNA results showed that inhibition of HSPA5 and MAT2A gene expression repressed growth of human cancer LNCaP cells. CONCLUSIONS: The current study globally assessed the transcriptome of the prostate and revealed the most abundant and tissue-specific transcripts which are responsible for the unique functions of this organ. These prostate-specific ARGs might be used as targets to develop safe and effective gene-based therapy for the prevention and treatment of prostate cancer.

Gender difference of androgen actions on skeletal muscle transcriptome.

Sarcopenia is related to metabolic syndrome in postmenopausal women. Hormone replacement therapies with androgens improve muscle functions by molecular mechanisms that are still unknown, at least partly because the skeletal muscle transcriptome has been less characterized in females. We performed the serial analysis of gene expression method in six experimental groups, intact (male and female), ovariectomy (OVX), OVX+dihydrotestosterone (DHT) injection 1, 3, or 24 h before kill in mice. The 438 transcript species differentially expressed between gender showed that females had higher expression levels of mRNA related to cytoskeleton/contractile apparatus and mitochondrial processes as well as protein, lipid, and amino acid metabolisms. In females, OVX and DHT modulated 109 and 128 transcript species respectively. OVX repressed transcripts of fast/glycolytic fiber, glycolysis, and glucose transport, whereas all these effects were reversed 3 h after the DHT injection. Moreover, DHT treatment induced transcripts which reduce intracellular Ca(2+) level at early time points. These results may suggest that DHT treatment in OVX mice increases muscle contractility by affecting fiber distribution and intracellular Ca(2+) concentration as well as improving glucose metabolism. On the other hand, transcripts of fast/oxidative fiber, oxidative phosphorylation, and ATP production were repressed 24 h after DHT administration. In our previous study using male mice, transcripts in oxidative phosphorylation and ATP production were induced 24 h after DHT injection (Yoshioka M, Boivin A, Ye P, Labrie F & St-Amand J 2006 Effects of dihydrotestosterone on skeletal muscle transcriptome in mice measured by serial analysis of gene expression. Journal of Molecular Endocrinology 36 247-259 ). These results demonstrate gender differences in DHT actions on skeletal muscle, and contribute to a precise understanding of the molecular mechanisms of androgen actions in the female skeletal muscle.

Maximum tolerable dose of red pepper decreases fat intake independently of spicy sensation in the mouth.

Dietary red pepper suppresses energy intake and modifies macronutrient intake. We have investigated whether a stimulus in the mouth and the sensation of spiciness are necessary for red pepper-induced changes in energy and macronutrient intake in human volunteers. In a preliminary test, sixteen Japanese male volunteers tasted samples of a soup with graded doses of red pepper in order to define a moderate and a maximum tolerable (strong) dose of red pepper. On the day of the experiment, a standardised breakfast was given to the volunteers. At lunchtime, the subjects ingested one of four experimental soups containing either a placebo, a moderate or a strong dose of red pepper plus placebo capsules, or a placebo soup plus capsules delivering a strong dose of red pepper. The rest of the meal was given ad libitum to all subjects. The amount of food, protein and carbohydrate ingested was similar for all conditions. Energy and fat intake were similar after the ingestion of the moderate soup compared with placebo. However, the strong soup significantly lowered fat intake compared with placebo (P=0.043), and ingestion of strong capsules also tended to suppress it (P=0.080). Moreover, energy intake after strong soup and capsules tended to be lower than placebo (P=0.089 and 0.076, respectively). The present results indicate that the maximum tolerable dose is necessary to have a suppressive effect of red pepper on fat intake. The main site of the action of red pepper is not in the mouth.

Resistance of adipose tissue lipoprotein lipase to insulin action in rats fed an obesity-promoting diet.

This study aimed to assess whether adipose lipoprotein lipase (LPL) becomes resistant to insulin in a nutritional model of resistance of glucose metabolism to insulin. Sprague-Dawley rats were fed for 4 wk chow or a purified high-sucrose, high-fat (HSHF) diet that induced overt insulin resistance. Rats were fasted for 24 h and then refed chow for 1, 3, or 6 h. The postprandial rise in insulinemia was similar in both dietary cohorts, whereas glycemia was higher in HSHF-fed than in chow-fed animals, indicating glucose intolerance and insulin resistance. In chow-fed rats, adipose LPL activity increased two- to fourfold postprandially, but only minimally (30%) in HSHF-fed rats. Muscle LPL decreased postprandially in HSHF-fed rats, suggesting intact sensitivity to insulin, but it increased in chow-fed animals. Peak postprandial triglyceridemia was higher (+70%) in insulin-resistant than in control rats. The postprandial rate of appearance of triglycerides in the circulation was similar in control and insulin-resistant rats, indicating that hypertriglyceridemia of the latter was the result of impaired clearance. These results demonstrate that adipose LPL becomes resistant to insulin in diet-induced IR and further suggest that, under certain nutritional conditions, modifications in adipose LPL modulation associated with insulin resistance, along with low muscle LPL, heightens postprandial hypertriglyceridemia through attenuated triglyceride clearance.