A low-carbohydrate high-fat diet increases weight gain and does not improve glucose tolerance, insulin secretion or ß-cell mass in NZO mice.

BACKGROUND/OBJECTIVES: Dietary guidelines for the past 20 years have recommended that dietary fat should be minimized. In contrast, recent studies have suggested that there could be some potential benefits for reducing carbohydrate intake in favor of increased fat. It has also been suggested that low-carbohydrate diets be recommended for people with type 2 diabetes. However, whether such diets can improve glycemic control will likely depend on their ability to improve ß-cell function, which has not been studied. The objective of the study was to assess whether a low-carbohydrate and therefore high-fat diet (LCHFD) is beneficial for improving the endogenous insulin secretory response to glucose in prediabetic New Zealand Obese (NZO) mice. METHODS: NZO mice were maintained on either standard rodent chow or an LCHFD from 6 to 15 weeks of age. Body weight, food intake and blood glucose were assessed weekly. Blood glucose and insulin levels were also assessed after fasting and re-feeding and during an oral glucose tolerance test. The capacity of pancreatic ß-cells to secrete insulin was assessed in vivo with an intravenous glucose tolerance test. ß-Cell mass was assessed in histological sections of pancreata collected at the end of the study. RESULTS: In NZO mice, an LCHFD reduced plasma triglycerides (P=0.001) but increased weight gain (P<0.0001), adipose tissue mass (P=0.0015), high-density lipoprotein cholesterol (P=0.044) and exacerbated glucose intolerance (P=0.013). Although fasting insulin levels tended to be higher (P=0.08), insulin secretory function in LCHFD-fed mice was not improved (P=0.93) nor was ß-cell mass (P=0.75). CONCLUSIONS: An LCHFD is unlikely to be of benefit for preventing the decline in ß-cell function associated with the progression of hyperglycemia in type 2 diabetes.

Sca13.

Spinocerebellar ataxia 13 (SCA13), initially described in a four-generation French family, has now also been characterized in a large Filipino pedigree. Ongoing investigations continue to identify additional SCA13 families and individuals. Recently, studies have shown that mutations in the voltage-gated potassium channel KCNC3 are causative for SCA13. Sequence analysis of KCNC3 revealed mutations 1554G-->A (R420H) in the Filipino and 1639C-->A (F448L) in the French pedigrees. Both mutations alter KCNC3 function in a Xenopus laevis oocyte expression system. KCNC3(R420H), located in the voltage sensor of the channel, has no detectable channel activity when expressed alone, and strong dominant negative effects when coexpressed with wild-type KCNC3. KCNC3(F448L) shifts the activation curve in the negative direction and causes an approximately sevenfold slowing of channel closure. These mutations are expected to change the output characteristics of fast-spiking cerebellar neurons, where KCNC channels confer capacity for high-frequency repetitive firing.

Nitrous oxide inhalation as a cause of cervical myelopathy.

Current evidence suggests that the incidence of recreational nitrous oxide inhalation is on the rise. Due to the possibility of clinically significant myelopathy, as well as potential response to treatment, it is important to consider this diagnosis when appropriate. We present a case of acquired ataxia and myelopathy due to nitrous oxide abuse and discuss diagnosis, pathophysiology, and response to treatment.

An autosomal dominant ataxia maps to 19q13: Allelic heterogeneity of SCA13 or novel locus?

The autosomal dominant spinocerebellar ataxias (ADCAs) represent a growing and heterogeneous disease phenotype. Clinical characterization of a three-generation Filipino family segregating a dominant ataxia revealed cerebellar signs and symptoms. After elimination of known spinocerebellar ataxia (SCA) loci, a genome-wide linkage scan revealed a disease locus in a 4-cM region of 19q13, with a 3.89 lod score. This region overlaps and reduces the SCA13 locus. However, this ADCA is clinically distinguishable from SCA13.

Cytokine-induced changes in chromatin structure and in vivo footprints in the inducible NOS promoter.

Transcription of the human inducible nitric oxide synthase (iNOS) gene is regulated by inflammatory cytokines in a tissue-specific manner. To determine whether differences in cytokine-induced mRNA levels between pulmonary epithelial cells (A549) and hepatic biliary epithelial cells (AKN-1) result from different protein or DNA regulatory mechanisms, we identified cytokine-induced changes in DNase I-hypersensitive (HS) sites in 13 kb of the iNOS 5'-flanking region. Data showed both constitutive and inducible HS sites in an overlapping yet cell type-specific pattern. Using in vivo footprinting and ligation-mediated PCR to detect potential DNA or protein interactions, we examined one promoter region near -5 kb containing both constitutive and cytokine-induced HS sites. In both cell types, three in vivo footprints were present in both control and cytokine-treated cells, and each mapped within a constitutive HS site. The remaining footprint appeared only in response to cytokine treatment and mapped to an inducible HS site. These studies, performed on chromatin in situ, identify a portion of the molecular mechanisms regulating transcription of the human iNOS gene in both lung- and liver-derived epithelial cells.

Induction of Th1 cytokine responses by mycobacterial antigens in leprosy.

Twelve mycobacterial antigens were compared for induction of gamma interferon (IFN-gamma) secretion by human blood mononuclear cells of patients with leprosy. Fractionated Mycobacterium leprae antigens containing cell wall proteins or cytosolic and membrane proteins induced good IFN-gamma responses in tuberculoid leprosy patients. Lipoarabinomannan from M. tuberculosis Erdman and M. leprae mycolylarabinogalactan peptidoglycan were the poorest IFN-gamma inducers.

Leprous neuropathies.

Once a terrifying disease, leprosy today has a very hopeful prognosis, provided that it is diagnosed early and treated with modern multidrug chemotherapy, any immunological reactions being recognized quickly and controlled well to prevent (further) peripheral nerve damage after commencing treatment. The diagnosis should be considered in all patients who present with peripheral neuropathy and/or anaesthetic skin lesions who come from or have lived in the tropics and subtropics. Although M. leprae cannot yet be grown in vitro, it is readily grown in experimental animals. A complete gene library has been developed, much of the genome mapped and a number species-specific and common mycobacterial antigens identified. The intricacies of the host-parasite relationship, especially of cell-mediated immunity, and of the important immunological reactions of ENL and reversal reaction have been widely investigated. Modern MDT has caused a dramatic fall in prevalence, although the world annual case detection rate remains at around 600,000 new patients, many being at an early stage of the disease. WHO has launched a campaign to eliminate leprosy as a significant public health risk by the 2000 (with a prevalence of less than 1:10 000 population), which may well be achieved in some endemic countries. Leprosy will, however, remain an important cause of peripheral neuropathy for at least several more decades.

Effect of Mycobacterium leprae in peripheral nerve trunk on the evolution of skin lesions.

Comparative histological studies were made of a) 41 peripheral nerve lesions and the skin in the area of supply, and b) 12 peripheral nerve lesions and concurrent but unrelated skin lesions. In the first study, small, relatively early, histologically classifiable skin lesions were found in all cases, even though there were no clinical lesions. In every case the lesion was centered on a dermal nerve. In some cases disruption of the perineurium was associated with emergence of the lesion into the dermis and a small silent local reaction. It was concluded that there was a descending spread of the disease down the neural pathway to the dermis, although it was not necessarily associated with transport of bacilli. Although the first study showed a discrepancy in the classification between skin and nerve lesions in nearly 50% of the cases (as previously reported), the second study showed no discrepancies. It is suggested that discrepancies are relatively uncommon, and that those in the first study are exceptional. The probable explanation is that microreactions in the nerve trunks had caused a shift in classification, which was not yet reflected in the immature skin lesions. In the second study, the mature skin lesions had reached immunological equilibrium. Discrepancies in classification between skin and nerve lesions, as between concurrent skin lesions, are the result of reaction. Attention is drawn to the probable role of subliminal reactions in the evolution of infections.

Difference in methylation patterns within the D15S9 region of chromosome 15q11-13 in first cousins with Angelman syndrome and Prader-Willi syndrome.

Abnormalities of chromosome region 15q11-13 are associated with Angelman syndrome (AS) and Prader-Willi syndrome (PWS). Differences between the methylation patterns of the region of chromosome 15q11-13 which hybridizes to the highly conserved DNA, DN34, in normal individuals and in patients with AS and PWS have been described. We report on a family in which first cousins are affected by AS and PWS as a result of a familial paracentric inversion of 15q11-q13. The results of the studies on this family demonstrate the differences in the methylation patterns in the 2 conditions and the phenomenon of genomic imprinting, whereby genetic information is expressed differently dependent on the parent of origin.

Chemotherapy of leprosy--current status and future prospects.

The introduction of multi-drug therapy (MDT) by the World Health Organization in 1982 has proved to be the most important advance in the management and control of leprosy since the first use of the sulphone drugs 40 years earlier. For the first time, the number of registered leprosy cases has shown a decline from a peak of 5.37 million in 1985 to 3.1 million in February 1992. The 2 standard MDT regimens have proved simple to apply in most parts of the world, are relatively cheap, generally acceptable, and have shown remarkably few toxic side-effects. Nevertheless, difficulties have arisen in distinguishing between multibacillary and paucibacillary leprosy, especially when skin smears are of poor quality. Relapses in paucibacillary leprosy have proved difficult to distinguish from late reversal reactions. In multibacillary leprosy, the duration of treatment, 2-10 years in lepromatous leprosy, is a source of difficulty, and in addition light-skinned patients dislike the skin discolouration caused by clofazimine, for fear that their diagnosis might be discovered. The discovery that 3 different groups of drugs are highly bactericidal for the leprosy bacillus, although not so rapidly bactericidal as rifampicin, raises the possibility of having simplified, shorter, or better supervised regimens in the future as second generation MDT. These drugs include the 4-fluoroquinolones, pefloxacin, ofloxacin and sparfloxacin, the tetracycline minocycline, and the macrolide clarithromycin. Finally, in low-prevalence areas it is opportune to consider chemoprophylaxis and immunoprophylaxis for child contacts of lepromatous patients.

Cytogenetic and molecular analysis in Angelman syndrome.

We report on cytogenetic and molecular analyses of 29 Angelman syndrome (AS) individuals ascertained in 1990 through the first National Angelman Syndrome Conference. High resolution GTG- and GBG-banded chromosomes were studied. Standard molecular analysis with six 15q11q13 DNA sequences was used to analyze copy number and parental origin of 15q11q13. Concordance between molecular and cytogenetic data was excellent. The combined data showed that 23 of the 27 probands (85%) on whom we had definitive results have deletions of the chromosome 15q11q13 region. Two classes of deletion were detected molecularly: most patients were deleted for the 5 more proximal probes, but in 2 cases the deletion extended distally to include in sixth probe. In the 13 cases where the parental origin of the deleted chromosome 15 could be established, it was maternal. There were no cases of uniparental disomy. Cytological observations of the relative sizes of the heterochromatic regions of the short arm of chromosome 15 suggested that chromosomes with large heterochromatic blocks may be more prone to de novo deletion.