Atypical expression of circadian clock genes in denervated mouse skeletal muscle

<div><p>The central circadian clock in the suprachiasmatic nucleus of the hypothalamus synchronizes peripheral clocks through neural and humoral signals in most mammalian tissues. Here, we analyzed the effects of unilateral sciatic denervation on the expression of circadian clock- and clock-controlled genes in the gastrocnemius muscles of mice twice per day on days 0, 3, 7, 9, 11 and 14 after denervation and six times on each of days 7 and 28 after denervation to assess the regulation mechanism of the circadian clock in skeletal muscle. Sciatic denervation did not affect systemic circadian rhythms since core body temperature (Day 7), corticosterone secretion (Days 7 and 28), and hepatic clock gene expression remained intact (Days 7 and 28). Expression levels of most circadian clock-related genes such as <i>Arntl, Per1, Rora, Nr1d1</i> and <i>Dbp</i> were reduced in accordance with the extent of muscle atrophy, although circadian <i>Per2</i> expression was significantly augmented (Day 28). Cosinor analysis revealed that the circadian expression of <i>Arntl</i> (Days 7 and 28) and <i>Dbp</i> (Day 28) was phase advanced in denervated muscle. The mRNA expression of <i>Clock</i> was significantly increased in denervated muscle on Day 3 when the severe atrophy was absent, and it was not affected by atrophic progression for 28 days. Sciatic denervation did not affect the expression of these genes in the contralateral muscle (Days 7 and 28), suggesting that humoral changes were not involved in denervation-induced muscle clock disruption. We then analyzed genome-wide gene expression using microarrays to determine the effects of disrupting the molecular clock in muscle on circadian rhythms at Day 7. Among 478 circadian genes, 313 lost rhythmicity in the denervated muscles. These denervation-sensitive genes included the lipid metabolism-related genes, <i>Nrip1, Bbs1, Ptgis, Acot1, Scd2, Hpgd, Insig1, Dhcr24, Ldlr</i> and <i>Mboat1</i>. Our findings revealed that sciatic denervation disrupts the circadian expression of clock and clock-controlled genes either directly or indirectly via muscle atrophy in the gastrocnemius muscles of mice in a gene-specific manner.</p></div

Wheat alkylresorcinols reduce micellar solubility of cholesterol <i>in vitro</i> and increase cholesterol excretion in mice

<p>Epidemiological studies have shown that the consumption of whole grains can reduce risk for metabolic disorders. We recently showed that chronic supplementation with wheat alkylresorcinols (ARs) prevents glucose intolerance and insulin resistance with hepatic lipid accumulation induced in mice by a high-fat high-sucrose diet (HFHSD). This study examines the effects of ARs on the micellar solubility of cholesterol <i>in vitro</i>, as well as the effects of transient AR supplementation on faecal lipid excretion and plasma lipid levels in mice. We found that ARs formed bile micelles with taurocholate independently of phospholipids, and dose-dependently decreased the micellar solubility of cholesterol in a biliary micelle model. Transient AR supplementation with HFHSD increased faecal cholesterol and triglyceride contents and decreased plasma cholesterol concentrations. These suggest that one underlying mechanism through which ARs suppress diet-induced obesity is by interfering with the micellar cholesterol solubilisation in the digestive tract, which subsequently decreases cholesterol absorption.</p

Wheat alkylresorcinols reduce micellar solubility of cholesterol <i>in vitro</i> and increase cholesterol excretion in mice

<p>Epidemiological studies have shown that the consumption of whole grains can reduce risk for metabolic disorders. We recently showed that chronic supplementation with wheat alkylresorcinols (ARs) prevents glucose intolerance and insulin resistance with hepatic lipid accumulation induced in mice by a high-fat high-sucrose diet (HFHSD). This study examines the effects of ARs on the micellar solubility of cholesterol <i>in vitro</i>, as well as the effects of transient AR supplementation on faecal lipid excretion and plasma lipid levels in mice. We found that ARs formed bile micelles with taurocholate independently of phospholipids, and dose-dependently decreased the micellar solubility of cholesterol in a biliary micelle model. Transient AR supplementation with HFHSD increased faecal cholesterol and triglyceride contents and decreased plasma cholesterol concentrations. These suggest that one underlying mechanism through which ARs suppress diet-induced obesity is by interfering with the micellar cholesterol solubilisation in the digestive tract, which subsequently decreases cholesterol absorption.</p

Reduced skin lipid content in obese Japanese women mediated by decreased expression of rate-limiting lipogenic enzymes

<div><p>Skin barrier function is often deficient in obese individuals, but the underlying molecular mechanisms remain unclear. This study investigated how skin structure and lipid metabolism, factors strongly associated with barrier function, differed among 50 Japanese women of greatly varying body mass index (BMI). Subjects receiving breast reconstruction surgery were chosen for analysis to obtain skin samples from the same site. The subjects were classified into two groups, control (BMI < 25 kg/m²) and obese (25 kg/m² ≤ BMI < 35 kg/m²), according to standards in Japan. Hematoxylin and eosin staining was used to assess skin thickness, Ki-67 immunostaining to examine keratinocyte proliferation, and real-time polymerase chain reaction to measure skin expression levels of genes associated with lipid metabolism. Total lipids, cholesterol, and fatty acids were also measured from these same skin samples. In the obese group, structural changes included epidermal thickening and an increase in the number of Ki-67-positive (proliferating) cells. Both skin cholesterol and fatty acid levels exhibited an “inverted-U” relationship with BMI, suggesting that there is an optimal BMI for peak lipid content and barrier function. Decreased lipid levels at higher BMI were accompanied by downregulated expression of <i>PPARδ</i> and other genes related to lipid metabolism, including those encoding acetyl-CoA carboxylase and HMG-CoA reductase, the rate-limiting enzymes for fatty acid and cholesterol synthesis, respectively. Thus, elevated BMI may lead to deficient skin barrier function by suppressing local lipid synthesis.</p></div

Levels of each lipid in the skin.

<p>Total lipids (a), cholesterol (b), and fatty acids (c) in the skin are compared between the control group (BMI < 25 kg/m², n = 39) and obesity group (25 kg/m² ≤ BMI < 35 kg/m², n = 11). Data are presented as mean ± SD. Statistical comparisons between the groups are performed using the unpaired Student’s <i>t</i>-test (**<i>p</i> < 0.01). (d-i) Spearman’s rank correlation coefficients (r) between BMI and each lipid for all subjects (d, g), subjects with BMI < 22 kg/m² (e, h), and subjects with BMI from 22–35 kg/m² (f, i) (**<i>p</i> < 0.01).</p

Correlation between gene expression and the amounts of each lipid in the skin.

<p>Correlation between gene expression and the amounts of each lipid in the skin.</p

Skin histology in control and obesity groups.

<p>(a, b) HE staining of skin samples from the control group (a. BMI < 25 kg/m²) and the obesity group (b. 25 ≤ BMI < 35 kg/m²) (bar = 50 μm). The arrows (↕) indicate epidermal thickness and the arrowheads (▲) show the unevenness of epidermal thickness. (c) Epidermal area (mm²) in the control group and the obesity group. (d) Frequency histogram of epidermal thickness in the control group and the obesity group. (e, f) Ki-67 staining in the control group (e) and obesity group (f) (bar = 50 μm). Reddish brown cells are Ki-67-positive, suggesting proliferation (↑: arrows). (g) Percentages of Ki-67-positive cells (Mib-1 index) in the control group and the obesity group. Data are presented as mean ± SD. Statistical comparisons between the groups are performed using unpaired Student’s <i>t</i>-test (*<i>p</i><0.05, **<i>p</i><0.01).</p

Expression levels of lipid metabolism gene in the control and the obesity group.

<p>Expression levels of lipid metabolism gene in the control and the obesity group.</p

Patient characteristics.

<p>Patient characteristics.</p

Correlation between gene expression and BMI.

<p>Correlation between gene expression and BMI.</p