Allatostatin-A neurons inhibit feeding behavior in adult Drosophila.

How the brain translates changes in internal metabolic state or perceived food quality into alterations in feeding behavior remains poorly understood. Studies in Drosophila larvae have yielded information about neuropeptides and circuits that promote feeding, but a peptidergic neuron subset whose activation inhibits feeding in adult flies, without promoting metabolic changes that mimic the state of satiety, has not been identified. Using genetically based manipulations of neuronal activity, we show that activation of neurons (or neuroendocrine cells) expressing the neuropeptide allatostatin A (AstA) inhibits or limits several starvation-induced changes in feeding behavior in adult Drosophila, including increased food intake and enhanced behavioral responsiveness to sugar. Importantly, these effects on feeding behavior are observed in the absence of any measurable effects on metabolism or energy reserves, suggesting that AstA neuron activation is likely a consequence, not a cause, of metabolic changes that induce the state of satiety. These data suggest that activation of AstA-expressing neurons promotes food aversion and/or exerts an inhibitory influence on the motivation to feed and implicate these neurons and their associated circuitry in the mechanisms that translate the state of satiety into alterations in feeding behavior.

A neuropeptide circuit that coordinates sperm transfer and copulation duration in Drosophila.

Innate behaviors are often executed in concert with accompanying physiological programs. How this coordination is achieved is poorly understood. Mating behavior and the transfer of sperm and seminal fluid (SSFT) provide a model for understanding how concerted behavioral and physiological programs are coordinated. Here we identify a male-specific neural pathway that coordinates the timing of SSFT with the duration of copulation behavior in Drosophila. Silencing four abdominal ganglion (AG) interneurons (INs) that contain the neuropeptide corazonin (Crz) both blocked SSFT and substantially lengthened copulation duration. Activating these Crz INs caused rapid ejaculation in isolated males, a phenotype mimicked by injection of Crz peptide. Crz promotes SSFT by activating serotonergic (5-HT) projection neurons (PNs) that innervate the accessory glands. Activation of these PNs in copulo caused premature SSFT and also shortened copulation duration. However, mating terminated normally when these PNs were silenced, indicating that SSFT is not required for appropriate copulation duration. Thus, the lengthened copulation duration phenotype caused by silencing Crz INs is independent of the block to SSFT. We conclude that four Crz INs independently control SSFT and copulation duration, thereby coupling the timing of these two processes.

Axon targeting in the Drosophila visual system.

The neuronal wiring of the Drosophila melanogaster visual system is constructed through an intricate series of cell-cell interactions. Recent studies have identified some of the gene regulatory and cytoskeletal signaling pathways responsible for the layer-specific targeting of Drosophila photoreceptor axons. Target selection decisions of the R1-R6 subset of photoreceptor axons have been found to be influenced by the nuclear factors Brakeless and Runt, and target selection decisions of the R7 subset of axons have been found to require the cell-surface proteins Ptp69d, Lar and N-cadherin. A role for the visual system glia in orienting photoreceptor axon outgrowth and target selection has also been uncovered.

Effects of atorvastatin versus other statins on fasting and postprandial C-reactive protein and lipoprotein-associated phospholipase A2 in patients with coronary heart disease versus control subjects.

The effects of atorvastatin (40 mg/day) versus placebo on fasting and postprandial plasma levels of high-sensitivity C-reactive protein (hs-CRP) and lipoprotein-associated phospholipase A2 (Lp-PLA2) were examined over 36 weeks in 84 patients who had coronary heart disease and low-density lipoprotein cholesterol levels >130 mg/dl and compared directly with the effects of fluvastatin, lovastatin, pravastatin, and simvastatin. Results were also compared with those obtained in age- and gender-matched control subjects (n = 84). Feeding increased median hs-CRP levels by 2% in patients (p = NS) and 22% in controls (p <0.01) and increased mean Lp-PLA2 values by 9% in patients (p = NS) but decreased values by 21% in controls (p <0.0001). Patients had 51% higher median hs-CRP values and 29% higher mean Lp-PLA2 values than did controls (p <0.05 for hs-CRP and Lp-PLA2) in the fasting state; however, Lp-PLA2 values were 62% higher (p <0.0001) in the fed state in patients compared with controls. Atorvastatin decreased median hs-CRP levels by 32% (p <0.01) and mean Lp-PLA2 values by 26% in patients (p <0.0001), with similar decreases in the fed state, and none of the other statins had any significant effect on these parameters. Change in Lp-PLA2 was significantly related to change in low-density lipoprotein cholesterol (p <0.01), with no significant relations with change in hs-CRP. Our data indicate greater differences in patients with coronary heart disease compared with controls in Lp-PLA2 in the fed state than in the fasting state and that atorvastatin is more effective than fluvastatin, lovastatin, pravastatin, or simvastatin for decreasing not only low-density lipoprotein cholesterol but also hs-CRP and Lp-PLA2.

Nutrient Sensor in the Brain Directs the Action of the Brain-Gut Axis in Drosophila.

Animals can detect and consume nutritive sugars without the influence of taste. However, the identity of the taste-independent nutrient sensor and the mechanism by which animals respond to the nutritional value of sugar are unclear. Here, we report that six neurosecretory cells in the Drosophila brain that produce Diuretic hormone 44 (Dh44), a homolog of the mammalian corticotropin-releasing hormone (CRH), were specifically activated by nutritive sugars. Flies in which the activity of these neurons or the expression of Dh44 was disrupted failed to select nutritive sugars. Manipulation of the function of Dh44 receptors had a similar effect. Notably, artificial activation of Dh44 receptor-1 neurons resulted in proboscis extensions and frequent episodes of excretion. Conversely, reduced Dh44 activity led to decreased excretion. Together, these actions facilitate ingestion and digestion of nutritive foods. We propose that the Dh44 system directs the detection and consumption of nutritive sugars through a positive feedback loop.

Comparisons of effects of statins (atorvastatin, fluvastatin, lovastatin, pravastatin, and simvastatin) on fasting and postprandial lipoproteins in patients with coronary heart disease versus control subjects.

The effects of atorvastatin at 20, 40, and 80 mg/day on plasma lipoprotein subspecies were examined in a randomized, placebo-controlled fashion over 36 weeks in 97 patients with coronary heart disease (CHD) with low-density lipoprotein (LDL) cholesterol levels of >130 mg/dl and compared directly with the effects of fluvastatin (n = 28), pravastatin (n = 22), lovastatin (n = 24), and simvastatin (n = 25). The effects of placebo and 40 mg/day of each statin were also examined in subjects with CHD with subjects in the fasting state and in the fed state 4 hours after a meal rich in saturated fat and cholesterol and compared with results in age- and gender-matched control subjects. At all doses tested in the fasting and fed states, atorvastatin was significantly (p <0.01) more effective in lowering LDL cholesterol and non-high-density lipoprotein (HDL) cholesterol than all other statins, and significantly (p <0.05) more effective than all statins, except for simvastatin, in lowering triglyceride and remnant lipoprotein (RLP) cholesterol. At 40 mg/day in the fasting state, atorvastatin was significantly (p <0.01) more effective than all statins, except for lovastatin and simvastatin, in lowering cholesterol levels in small LDL, and was significantly (p <0.05) more effective than all statins, except for simvastatin, in increasing cholesterol in large HDL and in lowering LDL particle numbers. Our data indicate that atorvastatin was the most effective statin tested in lowering cholesterol in LDL, non-HDL, and RLP in the fasting and fed states, and getting patients with CHD to established goals, with fluvastatin, pravastatin, lovastatin, and simvastatin having about 33%, 50%, 60%, and 85% of the efficacy of atorvastatin, respectively, at the same dose in the same patients.

Effects of atorvastatin on fasting and postprandial lipoprotein subclasses in coronary heart disease patients versus control subjects.

The effects of atorvastatin at 20, 40, and 80 mg/day on plasma lipoprotein subclasses were examined in a randomized, placebo-controlled fashion over 24 weeks in 103 patients in the fasting state who had coronary heart disease (CHD) with low-density lipoprotein (LDL) cholesterol levels >130 mg/dl. The effects of placebo and atorvastatin 40 mg/day were examined in 88 subjects with CHD in the fasting state and 4 hours after a meal rich in saturated fat and cholesterol. These findings were compared with results in 88 age- and gender-matched control subjects. Treatment at the 20, 40, and 80 mg/day dose levels resulted in LDL cholesterol reductions of 38%, 46%, and 52% (all p <0.0001), triglyceride reductions of 22%, 26%, and 30% (all p <0.0001), and high-density lipoprotein (HDL) cholesterol increases of 6%, 5%, and 3%, respectively (all p <0.05 at the 20- and 40-mg doses). The lowest total cholesterol/HDL cholesterol ratio was observed with the 80 mg/day dose of atorvastatin (p <0.0001 vs placebo). Remnant-like particle (RLP) cholesterol decreased 33%, 34%, and 32%, respectively (all p <0.0001). Lipoprotein(a) [Lp(a)] cholesterol decreased 9%, 16%, and 21% (all p <0.0001), although Lp(a) mass increased 9%, 8%, and 10%, respectively (all p <0.01). In the fed state, atorvastatin 40 mg/day normalized direct LDL cholesterol (29% below controls), triglycerides (8% above controls), and RLP cholesterol (10% below controls), with similar reductions in the fasting state. At this same dose level, atorvastatin treatment resulted in 39%, 35%, and 59% decreases in fasting triglyceride in large, medium, and small very LDLs, as well as 45%, 33%, and 47% reductions in cholesterol in large, medium, and small LDL, respectively, as assessed by nuclear magnetic resonance (all significant, p <0.05), normalizing these particles versus controls (77 cases vs 77 controls). Moreover, cholesterol in large HDL was increased 37% (p <0.001) by this treatment. Our data indicate that atorvastatin treatment normalizes levels of all classes of triglyceride-rich lipoproteins and LDL in both the fasting and fed states in patients with CHD compared with control subjects.

The Drosophila ortholog of vertebrate TRPA1 regulates thermotaxis.

Thermotaxis is important for animal survival, but the molecular identities of temperature sensors controlling this behavior have not been determined. We demonstrate dTRPA1, a heat-activated Transient Receptor Potential (TRP) family ion channel, is essential for thermotaxis in Drosophila. dTrpA1 knockdown eliminates avoidance of elevated temperatures along a thermal gradient. We observe dTRPA1 expression in cells without previously ascribed roles in thermosensation and implicate dTRPA1-expressing neurons in mediating thermotaxis. Our data suggest that thermotaxis relies upon neurons and molecules distinct from those required for high-temperature nociception. We propose dTRPA1 may control thermotaxis by sensing environmental temperature.

Compartmentalization of visual centers in the Drosophila brain requires Slit and Robo proteins.

Brain morphogenesis depends on the maintenance of boundaries between populations of non-intermingling cells. We used molecular markers to characterize a boundary within the optic lobe of the Drosophila brain and found that Slit and the Robo family of receptors, well-known regulators of axon guidance and neuronal migration, inhibit the mixing of adjacent cell populations in the developing optic lobe. Our data suggest that Slit is needed in the lamina to prevent inappropriate invasion of Robo-expressing neurons from the lobula cortex. We show that Slit protein surrounds lamina glia, while the distal cell neurons in the lobula cortex express all three Drosophila Robos. We examine the function of these proteins in the visual system by isolating a novel allele of slit that preferentially disrupts visual system expression of Slit and by creating transgenic RNA interference flies to inhibit the function of each Drosophila Robo in a tissue-specific fashion. We find that loss of Slit or simultaneous knockdown of Robo, Robo2 and Robo3 causes distal cell neurons to invade the lamina, resulting in cell mixing across the lamina/lobula cortex boundary. This boundary disruption appears to lead to alterations in patterns of axon navigation in the visual system. We propose that Slit and Robo-family proteins act to maintain the distinct cellular composition of the lamina and the lobula cortex.