Ingestion Of Blood Meal Research Articles

Experimental Exposure of Swallow Bugs (Hemiptera: Cimicidae) to West Nile Virus

The cliff swallow (Petrochelidon pyrrhonota, Vieillot) could potentially play an important role in the transmission of West Nile virus (WNV) because of its breeding ecology, reservoir competence status, and potentially high natural exposure rates. These birds nest in colonies and their nests are occupied year round by swallow bugs (Oeciacus vicarius, Hovarth), hematophagus ectoparasites that feed primarily on cliff swallows. Swallow bugs are most likely exposed to WNV while feeding on infectious blood of cliff swallows and, thus, if competent vectors, could contribute to initiation and maintenance of seasonal WNV transmission. In addition, swallow bugs remain within nests year round and, therefore, if persistently infected and competent vectors, they could provide an overwintering mechanism for WNV. We tested the hypothesis that swallow bugs become infected with WNV through direct abdominal inoculation or ingestion of infectious blood meals. We observed that swallow bugs did not maintain or amplify WNV, and infectious virus titers within bugs declined over 15 d postexposure. These results suggest that swallow bugs may not be competent vectors of WNV, and therefore are unlikely to play a significant role in transmission.

Plasmodium infection alters Anopheles gambiae detoxification gene expression

BackgroundAnopheles gambiae has been shown to change its global gene expression patterns upon Plasmodium infection. While many alterations are directly related to the mosquito's innate immune response, parasite invasion is also expected to generate toxic by-products such as free radicals. The current study aimed at identifying which loci coding for detoxification enzymes are differentially expressed as a function of Plasmodium berghei infection in midgut and fat body tissues.ResultsUsing a custom-made DNA microarray, transcript levels of 254 loci primarily belonging to three major detoxification enzyme families (glutathione S-transferases, cytochrome P450 monooxygenases and esterases) were compared in infected and uninfected mosquitoes both during ookinete invasion and the release of sporozoites into the hemocoel. The greatest changes in gene expression were observed in the midgut in response to ookinete invasion. Interestingly, many detoxification genes including a large number of P450s were down-regulated at this stage. In the fat body, while less dramatic, gene expression alterations were also observed and occurred during the ookinete invasion and during the release of sporozoites into the hemocoel. While most gene expression changes were tissue-related, CYP6M2, a CYP previously associated with insecticide resistance, was over-expressed both in the midgut and fat body during ookinete invasion.ConclusionsMost toxicity-related reactions occur in the midgut shortly after the ingestion of an infected blood meal. Strong up-regulation of CYP6M2 in the midgut and the fat body as well as its previous association with insecticide resistance shows its broad role in metabolic detoxification.

Chicken blood provides a suitable meal for the sand fly Lutzomyia longipalpis and does not inhibit Leishmania development in the gut

BackgroundThe aim of this study was to address the role of chickens as bloodmeal sources for female Lutzomyia longipalpis and to test whether chicken blood is harmful to Leishmania parasite development within the sand flies. Bloodmeal ingestion, excretion of urate, reproduction, fecundity, as well as Leishmania infection and development were compared in sand flies fed on blood from chickens and different mammalian sources.ResultsLarge differences in haemoglobin and protein concentrations in whole blood (dog>human>rabbit> chicken) did not correlate with differences in bloodmeal protein concentrations (dog = chicken>human>rabbit). This indicated that Lu. longipalpis were able to concentrate bloodmeals taken from different hosts using prediuresis and this was confirmed by direct observation. Sand flies fed on chickens or dogs produced significantly more eggs than those fed on human blood. Female Lu. longipalpis retained significantly more urate inside their bodies when fed on chicken blood compared to those fed on rabbit blood. However, when the amounts of urate excreted after feeding were measured, sand flies fed on rabbit blood excreted significantly more than those fed on chicken blood. There was no difference in female longevity after feeding on avian or mammalian blood.Sand flies infected via chicken blood produced Leishmania mexicana infections with a similar developmental pattern but higher overall parasite populations than sand flies infected via rabbit blood.ConclusionsThe results of this study help to define the role that chickens play in the epidemiology of leishmaniasis. The present study using a Lu. longipalpis/L. mexicana model indicates that chickens are suitable hosts to support a Lu. longipalpis population and that chicken blood is likely to support the development of transmissible Leishmania infections in Lu. longipalpis.

Nutritional stress affects the tsetse fly's immune gene expression

Tsetse-transmitted trypanosomiasis poses a serious threat to human and animal health in sub-Saharan Africa. The majority of tsetse flies (Glossina spp.) in a natural population will not develop a mature infection of either Trypanosoma congolense or Trypanosoma brucei sp. because of refractoriness, a phenomenon that is affected by different factors, including the tsetse fly's immune defence. Starvation of tsetse flies significantly increases their susceptibility to the establishment of a trypanosome infection. This paper reports the effects of nutritional stress (starvation) on (a) uninduced baseline levels of gene expression of the antimicrobial peptides attacin, defensin and cecropin in the tsetse fly, and (b) levels of expression induced in response to bacterial (Escherichia coli) or trypanosomal challenge. In newly emerged, unfed tsetse flies, starvation significantly lowers baseline levels of antimicrobial peptide gene expression, especially for attacin and cecropin. In response to trypanosome challenge, only non-starved older flies showed a significant increase in antimicrobial peptide gene expression within 5 days of ingestion of a trypanosome-containing bloodmeal, especially with T. brucei bloodstream forms. These data suggest that a decreased expression of immune genes in newly hatched flies or a lack of immune responsiveness to trypanosomes in older flies, both occurring as a result of fly starvation, may be among the factors contributing to the increased susceptibility of nutritionally stressed tsetse flies to trypanosome infection.

Outer surface protein A protects Lyme disease spirochetes from acquired host immunity in the tick vector.

The Lyme disease spirochete Borrelia burgdorferi alters the expression of outer surface protein (osp) genes as the bacterium cycles between ticks and mammals. OspA is produced as borreliae enter the tick vector and remains a major surface antigen during midgut colonization. To elucidate the role of OspA in the vector, we created an insertional deletion of ospA in strain B31-A3. The ospA mutant infects mice when it is injected intradermally and is acquired by larval ticks fed on these mice, where it persists through the molt to the nymph stage. Bacterial survival rates in artificially infected tick larvae fed on naïve mice were compared with those in the vector fed on immune mice. The ospA mutant proliferates in larvae if it is exposed to blood from naïve mice, but it declines in density after larval feeding if the blood is from immune mice. When uninfected larvae are fed on B-cell-deficient mice infected with the ospA mutant, larvae show borrelial densities and persistence that are significantly greater than those fed on infected, immunocompetent mice. We conclude that OspA serves a critical antibody-shielding role during vector blood meal uptake from immune hosts and is not required for persistence in the tick vector.

Gene silencing in phlebotomine sand flies: Xanthine dehydrogenase knock down by dsRNA microinjections

Lutzomyia longipalpis are vectors of medically important visceral leishmaniasis in South America. Blood-fed adult females digest large amounts of protein, and xanthine dehydrogenase is thought to be a key enzyme involved in protein catabolism through the production of urate. Large amounts of heme are also released during digestion with potentially damaging consequences, as heme can generate oxygen radicals that damage lipids, proteins and nucleic acids. However, urate is an antioxidant that may prevent such oxidative damage produced by heme. We investigated xanthine dehydrogenase by developing the RNAi technique for sand flies and used this technique to knock down the Lu. longipalpis xanthine dehydrogenase gene to evaluate its role in survival of adult females after blood feeding. The gene sequence of Lu. longipalpis xanthine dehydrogenase is described together with expression in different life cycle stages and RNAi knock down. Semi-quantitative RT-PCR of xanthine dehydrogenase expression showed a significant increase in expression after bloodmeal ingestion. Microinjection of dsRNA via the thorax of 1-day-old adult female sand flies resulted in approximately 40% reduction of xanthine dehydrogenase gene expression in comparison to flies injected with a control dsRNA. A significant reduction of urate in the whole body and excretions of Lu. longipalpis was observed after dsRNA xanthine dehydrogenase microinjection and feeding 96 h later on rabbit blood. Sand flies injected with XDH dsRNA also exhibit significantly reduced life span in comparison with the mock-injected group when fed on sucrose or when rabbit blood fed, showing that urate could be indeed an important free radical scavenger in Lu. longipalpis. The demonstration of xanthine dehydrogenase knock down by dsRNA microinjection, low mortality of microinjected insects and the successful bloodfeeding of injected insects demonstrated the utility of RNAi as a tool for functional analysis of genes in phlebotomine sand flies.

Experimental Infection of Aedes sollicitans and Aedes taeniorhynchus with Two Chimeric Sindbis/Eastern Equine Encephalitis Virus Vaccine Candidates

Two chimeric vaccine candidates for Eastern equine encephalitis virus (EEEV) were developed by inserting the structural protein genes of either a North American (NA) or South American (SA) EEEV into a Sindbis virus (SINV) backbone. To assess the effect of chimerization on mosquito infectivity, experimental infections of two potential North American bridge vectors of EEEV, Aedes sollicitans and Ae. taeniorhynchus, were attempted. Both species were susceptible to oral infection with all viruses after ingestion of high titer blood meals of ca. 7.0 log(10) plaque-forming units/mL. Dissemination rates for SIN/NAEEEV (0 of 56) and SIN/SAEEEV (1 of 54) were low in Ae. taeniorhynchus and no evidence of transmission potential was observed. In contrast, the chimeras disseminated more efficiently in Ae. sollicitans (19 of 68 and 13 of 57, respectively) and were occasionally detected in the saliva of this species. These results indicate that chimerization of the vaccine candidates reduces infectivity. However, its impact on dissemination and potential transmission is mosquito species-specific.

Selective Cysteine Protease Inhibition Contributes to Blood-feeding Success of the Tick Ixodes scapularis

Ixodes scapularis is the main vector of Lyme disease in the eastern and central United States. Tick salivary secretion has been shown as important for both blood-meal completion and pathogen transmission. Here we report a duplication event of cystatin genes in its genome that results in a transcription-regulated boost of saliva inhibitory activity against a conserved and relatively limited number of vertebrate papain-like cysteine proteases during blood feeding. We further show that the polypeptide products of the two genes differ in their binding affinity for some enzyme targets, and they display different antigenicity. Moreover, our reverse genetic approach employing RNA interference uncovered a crucial mediation in tick-feeding success. Given the role of the targeted enzymes in vertebrate immunity, we also show that host immunomodulation is implicated in the deleterious phenotype of silenced ticks making I. scapularis cystatins attractive targets for development of anti-tick vaccines.

Spatial and Temporal Population Dynamics of a Naturally Occurring Two-Species Microbial Community inside the Digestive Tract of the Medicinal Leech

The medicinal leech, Hirudo verbana, is one of the simplest naturally occurring models for digestive-tract symbioses, where only two bacterial species, Aeromonas veronii bv. sobria (gamma-Proteobacteria) and a Rikenella-like bacterium (Bacteroidetes), colonize the crop, the largest compartment of the leech digestive tract. In this study, we investigated spatial and temporal changes of the localization and microcolony structure of the native symbionts in the crop, after ingestion of a sterile blood meal, by fluorescence in situ hybridization. The population dynamics differed between the two symbiotic bacteria. A. veronii was detected mainly as individual cells inside the intraluminal fluid (ILF) during 14 days after feeding (daf) unless it was found in association with Rikenella microcolonies. The Rikenella-like bacteria were observed not only inside the ILF but also in association with the luminal surface of the crop epithelium. The sizes of Rikenella microcolonies changed dynamically through the 14-day period. From 3 daf onward, mixed microcolonies containing both species were frequently observed, with cells of both species tightly associating with each other. The sizes of the mixed microcolonies were consistently larger than the size of either single-species microcolony, suggesting a synergistic interaction of the symbionts. Lectin staining with succinylated wheat germ agglutinin revealed that the planktonic microcolonies present in the ILF were embedded in a polysaccharide matrix containing N-acetylglucosamine. The simplicity, symbiont-symbiont interaction, and mixed microcolonies of this naturally occurring, digestive-tract symbiosis lay the foundation for understanding the more complex communities residing in most animals.

Involvement of actin and myosins in Plasmodium berghei ookinete motility

Ookinetes of the genus Plasmodium are motile, invasive cells that develop in the mosquito midgut following ingestion of a parasite-infected blood meal. We show here that ookinetes display gliding motility on glass slides in the presence of insect cells. Moreover, in addition to stationary “flexing” and “twirling” of the cells, two distinct types of movements occur: productive forward translocational motility in straight segment that progresses with an average speed of approximately 6μm/min and rotational motility, which does not lead to forward translocation. Locomotion is reduced by treatment with butanedione monoxime, an inhibitor of myosin ATPase, and by three different actin inhibitors. We also studied the expression during ookinete development of genes encoding actin and two small class XIV myosins, PbMyoA, and PbMyoB. Western immunoblots revealed that PbMyoA is only present in fully mature ookinetes, whilst the other two proteins are additionally expressed in gametocytes and zygotes. Immunofluorescence experiments reveal that MyoA and actin co-localize in the apical tip of the parasite whereas MyoB displays a punctate pattern of expression around the entire cell periphery. Following treatment with jasplakinolide, the apparent level of detectable actin appears to substantially increase and becomes concentrated in a discrete area in the basal pole of the ookinete.

A novel secreted endonuclease from Culex quinquefasciatussalivary glands

Previous analysis of the salivary gland transcriptome of Culex quinquefasciatus showed the potential presence of an endonuclease with sequence similarities to shrimp, crab and two tsetse salivary proteins. Indeed, not only was the cloned cDNA shown to encode an active double-stranded endonuclease, but also the same activity was demonstrated to be secreted by salivary glands of Cx. quinquefasciatus. Preliminary studies with salivary gland extracts confirmed the presence of a highly active nuclease. This enzyme was shown to be present in the saliva of female mosquitoes by allowing starved mosquitoes to probe DNA-containing agarose gel. The recombinant Cx. quinquefasciatus endonuclease (CuquEndo) produced in mammalian cells showed no sequence specificity for DNA substrate except that it only cleaves double-stranded DNA. Recombinant Cx. quinquefasciatus endonuclease was active in the presence of Mg(2+) ions at pH 7.0-8.0, but no endonuclease activity was detected in the presence of calcium ions. The final hydrolysis products of this enzyme, detected by ion exchange chromatography, yielded DNA fragments ranging form 8-12 base pairs. Although endonucleases have been associated with a variety of cellular functions, their role in mosquito saliva is not clear. This female-specific secreted endonuclease may assist blood meal intake by lowering the local viscosity created by the release of host DNA in the bite site and/or acting as an indirect anticoagulant factor by producing a defibrotide-like mixture of DNA haptamers.

Molecular Characterization of Two Novel Antibacterial Peptides Inducible upon Bacterial Challenge in an Annelid, the Leech Theromyzon tessulatum

Two novel antimicrobial peptides named theromacin and theromyzin were isolated and characterized from the coelomic liquid of the leech Theromyzon tessulatum. Theromacin is a 75-amino acid cationic peptide containing 10 cysteine residues arranged in a disulfide array showing no similarities with other known antimicrobial peptides. Theromyzin is an 86-amino acid linear peptide and constitutes the first anionic antimicrobial peptide observed in invertebrates. Both peptides exhibit activity directed against Gram-positive bacteria. Theromacin and theromyzin cDNAs code precursor molecules containing a putative signal sequence directly followed by the mature peptide. The enhancement of theromacin and theromyzin mRNA levels has been observed after blood meal ingestion and upon bacterial challenge. In situ hybridization revealed that both genes are expressed in large fat cells in contact with coelomic cavities. Gene products were immunodetected in large fat cells, in intestinal epithelia, and at the epidermis level. In addition, a rapid release of the peptides into the coelomic liquid was observed after bacterial challenge. The presence of antimicrobial peptide genes in leeches and their expression in a specific tissue functionally resembling the insect fat body provide evidence for the first time of an antibacterial response in a lophotrochozoan comparable to that of holometabola insects.

A targeted approach to the identification of candidate genes determining susceptibility to Plasmodium gallinaceum in Aedes aegypti.

The malaria parasite, Plasmodium, has evolved an intricate life cycle that includes stages specific to a mosquito vector and to the vertebrate host. The mosquito midgut represents the first barrier Plasmodium parasites encounter following their ingestion with a blood meal from an infected vertebrate. Elucidation of the molecular interaction between the parasite and the mosquito could help identify novel approaches to preventing parasite development and subsequent transmission to vertebrates. We have used an integrated Bulked Segregant Analysis-Differential Display (BSA-DD) approach to target genes expressed that are in the midgut and located within two genome regions involved in determining susceptibility to P. gallinaceum in the mosquito Aedes aegypti. A total of twenty-two genes were identified and characterized, including five genes with no homologues in public sequence databases. Eight of these genes were mapped genetically to intervals on chromosome 2 that contain two quantitative trait loci (QTLs) that determine susceptibility to infection by P. gallinaceum. Expression analysis revealed several expression patterns, and ten genes were specifically or preferentially expressed in the midgut of adult females. Real-time PCR quantification of expression with respect to the time of blood meal ingestion and infection status in mosquito strains permissive and refractory for malaria revealed a differential expression pattern for seven genes. These represent candidate genes that may influence the ability of the mosquito vector to support the development of Plasmodium parasites. Here we describe their isolation and discuss their putative roles in parasite-mosquito interactions and their use as potential targets in strategies designed to block transmission of malaria.

Molecular characterization of three gut genes from Glossina morsitans morsitans: cathepsin B, zinc-metalloprotease and zinc-carboxypeptidase.

Insect gut enzymes are involved in digestion of dietary proteins. Additionally, these enzymes have been implicated in the process of pathogen establishment in several insects including the tsetse fly (Diptera:Glossinidae), which is the vector for African trypanosomes. Both the male and female tsetse can transmit trypanosomes and are strict blood feeders during all stages of their development. Here, we describe the molecular characterization of three gut genes: cathepsin B (GmCatB), zinc-metalloprotease (GmZmp) and zinc-carboxypeptidase (GmZcp). The cDNA for GmCatB encodes a protein for 340 amino acids with a predicted molecular mass of 38.2 kDa, while the 854 bp GmZmp cDNA encodes a protein of 254 amino acids with a molecular mass of 29 kDa. The GmZcp cDNA is 1319 bp in length and has a 354 amino acids open reading frame for coding a 40 kDa protein. All three cDNAs have signal peptide sequences associated with their N-terminal domains and structure analysis indicates that GmCatB and GmZmp are expressed as zymogens with pro-domains proteolytically removed for activity. The activation domain associated with the carboxypeptidase sequences is lacking in GmZcp. While GmCatB transcription is constitutive, teneral flies express very low levels of transcripts for GmZmp and GmZcp prior to the first bloodmeal. Transcription of all genes is induced and remains high throughout the digestion cycle within a few hours following the first bloodmeal ingestion. Both GmCatB and GmZcp are parasite responsive, with the expression of both genes being higher in trypanosome infected flies.

Identification of a polymorphic mucin-like gene expressed in the midgut of the mosquito, Aedes aegypti, using an integrated bulked segregant and differential display analysis.

The identification of putative differentially expressed genes within genome regions containing QTL determining susceptibility of the mosquito, Aedes aegypti, to the malarial parasite, Plasmodium gallinaceum, was investigated using an integrated, targeted approach based on bulked segregant and differential display analysis. A mosquito F2 population was obtained from pairwise matings between the parasite-susceptible RED strain and the resistant MOYO-R substrain. DNA from female carcasses was used to genotype individuals at RFLP markers of known chromosomal position around the major QTL (pgs 1). Midguts, dissected 48 hr after an infected blood meal, were used to prepare two RNA bulks, each representing one of the parental genotypes at the QTL interval. The RNA bulks were compared by differential display PCR. A mucin-like protein gene (AeIMUC1) was isolated and characterized. The gene maps within the pgs 1 QTL interval and is expressed in the adult female midgut. AeIMUC1 RNA abundance decreased with time after blood meal ingestion. No differential expression was observed between the two mosquito strains but three different alleles with inter- and intrastrain allelic polymorphisms including indels and SNPs were characterized. The AeIMUC1 gene chromosome location and allelic polymorphisms raise the possibility that the protein might be involved in parasite-mosquito interactions.

Effect of xanthurenic acid on infectivity of Plasmodium falciparum to Anophelesstephensi

Terminally differentiated malarial gametocytes remain in the vertebrate circulation in a developmentally arrested state until they are taken up by the mosquito. The gametocytes then undergo gametogenesis in the mosquito mid-gut within minutes after ingestion of the infected blood meal. The male gametogenesis (exflagellation) can be triggered by the combination of a decrease in temperature of at least 5°C and a simultaneous increase in pH between 8.0 and 8.3. Xanthurenic acid, which is present in mosquito mid-gut as well as in mosquito head, had been shown to induce exflagellation in vitro at a non-permissible pH. Here we report for the first time that with the increasing concentration of exogeneous xanthurenic acid, there is a gradual increase in the number of oocysts in the mid-gut of infected mosquitoes. The concentration of xanthurenic acid for optimum infection in the membrane feeding assay was determined to be 100 μM. Three different strains of Plasmodium falciparum, viz. 3D7, 7G8 and W2 were tested in different experiments and similar findings hold true for all of them. These results demonstrate that xanthurenic acid not only induces exflagellation of male gametocytes but also promotes infectivity of Plasmodium falciparum to mosquito vectors.

Anti-mosquito midgut antibodies block malaria transmission

Vector competence is the innate suitability of an invertebrate for the development of a parasite, so enabling completion of the latter's lifecycle. The reduction of vector competence is the main objective of two fast-moving areas of research on vector-borne diseases, namely transmission-blocking (T-B) immunity and replacement of natural vector populations with those genetically engineered for refractoriness. For malaria, T-B immunity is thought to inhibit development of the parasite, Plasmodium, within the midgut of its Anopheles mosquito vector. Following ingestion of an infective blood meal, first fertilization occurs and then the resulting zygote transforms into a motile ookinete. This stage escapes the hostile environment of the midgut by wedging between the basal lamina and midgut epithelium, where it encysts and develops into a sporozoite-producing oocyst. The ookinete-to-oocyst transition is considered the weakest link in sporogonic development. Hence, the rationale for current T-B vaccine strategies is to target Plasmodium while within and traversing the mosquito midgut.

Effect of a second bloodmeal on the oesophagus colonization by Leishmania mexicana complex in Lutzomyia evansi (Diptera: Psychodidae).

Migration and colonization of the oesophagus by Leishmania mexicana parasites were enhanced after digestion of a second bloodmeal intake in Lutzomyia evansi. This event has epidemiological significance since it affects the infection susceptibility of this sand fly species, which is a proven vector of L. chagasi in Colombian and Venezuelan visceral leishmaniasis foci. Also, it may explain the host seeking behaviour displayed by some partially bloodfed flies found inside houses.

Growth characteristics of the chimeric Japanese encephalitis virus vaccine candidate, ChimeriVax-JE (YF/JE SA14--14--2), in Culex tritaeniorhynchus, Aedes albopictus, and Aedes aegypti mosquitoes.

The Japanese encephalitis (JE) virus vaccine candidate, ChimeriVax-JE, which consists of a yellow fever (YF) 17D virus backbone containing the prM and E genes from the JE vaccine strain JE SA14--14--2, exhibits restricted replication in non-human primates, producing only a low-level viremia following peripheral inoculation. Although this reduces the likelihood that hematophagous insects could become infected by feeding on a vaccinated host, it is prudent to investigate the replication kinetics of the vaccine virus in mosquito species that are known to vector the viruses from which the chimera is derived. In this study ChimeriVax-JE virus was compared to its parent viruses, as well as to wild-type JE virus, for its ability to replicate in Culex tritaeniorhynchus, Aedes albopictus, and Aedes aegypti mosquitoes. Individual mosquitoes were exposed to the viruses by oral ingestion of a virus-laden blood meal or by intrathoracic (IT) virus inoculation. ChimeriVax-JE virus did not replicate following ingestion by any of the three mosquito species. Additionally, replication was not detected after IT inoculation of ChimeriVax-JE in the primary JE virus vector, Cx. tritaeniorhynchus. ChimeriVax-JE exhibited moderate growth following IT inoculation into Ae. aegypti and Ae. albopictus, reaching titers of 3.6-5.0 log(10) PFU/mosquito. There was no change in the virus genotype associated with replication in mosquitoes. Similar results were observed in mosquitoes of all three species that were IT inoculated or had orally ingested the YF 17D vaccine virus. In contrast, all mosquitoes either IT inoculated with or orally fed wild-type and vaccine JE viruses became infected, reaching maximum titers of 5.4-7.3 log(10) PFU/mosquito. These results indicate that ChimeriVax-JE virus is restricted in its ability to infect and replicate in these mosquito vectors. The low viremia caused by ChimeriVax-JE in primates and poor infectivity for mosquitoes are safeguards against secondary spread of the vaccine virus.

Determinants of post-ischaemic reactive hyperaemia in patients with diabetes mellitus type II.

Dysfunction of resistance arteries is thought to be an early reversible stage in the development of atherosclerosis. Dynamics of post-ischaemic reactive hyperaemia are believed to constitute a useful tool for monitoring resistance vessel function. Patient characteristics influencing reactive hyperaemia, however, need to be defined more precisely. Since reactive hyperaemia is a dynamic process, yielding submaximal peak values after 5 min of ischaemia, this period was chosen to investigate the determinants of reactive hyperaemia in 100 type II diabetic patients as well as in 61 control subjects. Reactive hyperaemia was measured by venous-occlusion plethysmography; clinical and laboratory data were acquired by routine methods. Statistical comparison was performed with SYSTAT 5.0 for Apple Macintosh. Overall, no significant differences between diabetic patients and controls were observed by group comparison. In control subjects, only gender showed an influence on peak reactive hyperaemia (females 40.5 +/- 15.3; males 51.8 +/- 17.7 ml min-1 100 ml-1, P < 0.01). In diabetic patients, in addition to gender, actual blood glucose (r = 0.377, P < 0.05) and meal intake (non-fasting 42.8 +/- 19.2; fasting 51.2 +/- 19.5 ml min-1 100 ml-1, P < 0.05) were found to influence reactive hyperaemia. Further investigation revealed a loss of the correlation between peak reactive hyperaemia and actual blood glucose observed in the fasting state (P < 0.001) in non-fasting diabetic patients, indicating an influence of meal intake on resistance vessel reactivity. Our results suggest that, in diabetic subjects, in addition to gender actual blood glucose and the postprandial situation impacts on peak reactive hyperaemia.