The effect of glucosamine on glucose metabolism in humans: a systematic review of the literature.

OBJECTIVE: Glucosamine is commonly used for the treatment of osteoarthritis. It is available as an over the counter preparation and also as a prescription pharmaceutical. There is concern from animal experiments that glucosamine may alter glucose metabolism through the hexosamine biosynthetic pathway. The objective of this systematic review is to determine if exogenous glucosamine adversely affects glucose metabolism in humans. This review does not separate out the effects on glucose metabolism of the various glucosamine preparations. METHOD: An English-language literature search of MEDLINE, EMBASE and EBM Reviews (1950-February 2009) was conducted. The bibliographies of selected papers were manually searched for additional references. Two reviewers independently analyzed studies for quality and content using a standardized data extraction form. RESULTS: Eleven studies were included. Six studies were randomized controlled trials and the remaining five were prospective studies with or without controls. Four of the studies found decreased insulin sensitivity or increased fasting glucose in subjects taking glucosamine. Three of these were clinical studies using oral glucosamine. Studies that included subjects with baseline impaired glucose tolerance or insulin resistance were more likely to detect an effect on glucose metabolism than studies without such subjects. CONCLUSION: Clinical studies, including three using oral glucosamine, have provided mixed evidence about the effect of exogenous glucosamine on glucose metabolism in humans. Therefore, more studies are needed, particularly including subjects at high risk for impairments in glucose homeostasis, before a definite conclusion can be made.

Functional testosterone: biochemical assessment of hypogonadism in men--report from a multidisciplinary workshop hosted by the Ontario Society of Clinical Chemists.

OBJECTIVES: In 2004, the Ontario Society of Clinical Chemists (OSCC) held an invitational multidisciplinary workshop to establish the most reliable, cost-effective approach to the biochemical assessment of hypogonadism in men. METHODS: Specialists across Canada in clinical biochemistry, endocrinology, family medicine and urology were invited to participate in this workshop which included individual presentations and a consensus component addressing two challenge statements: 1) 'Determinations for total testosterone (TT) are equivalent to those for bioavailable testosterone (BAT) or calculated BAT (cBAT) or free testosterone (FT) (by analogue radioimmunoassay or equilibrium dialysis) or calculated FT (cFT)'; 2) 'There is no good evidence that borderline low testosterone concentrations in men should be treated'. The main outcomes were to identify what agreement exists in Canada, what issues were still controversial, and what research remains to be addressed. RESULTS: Six recommendations based on expert opinion addressed these main themes: investigate with morning total testosterone (TT) followed by repetition and reflexive testing of sex hormone binding globulin (SHBG) if testosterone is 8-15 nmol/L with automatic calculation of cBAT; discontinue the use of analogue free testosterone assays; and definitive methods and standards must be available to ensure standardized results. CONCLUSIONS: Total testosterone is a reliable marker for the initial investigation of men presenting with symptoms of hypogonadism; cBAT is a reasonable follow-up test in patients with equivocal biochemical or consistent symptomatic findings.

Protocols for the use of cyproterone, medroxyprogesterone, and leuprolide in the treatment of paraphilia.

OBJECTIVE: To propose a protocol for minimizing medical complications associated with the use of cyproterone, medroxyprogesterone, and depot leuprolide to treat paraphilia. METHOD: Review of the relevant literature. RESULTS: Certain patient populations should not be treated with these medications, and medical complications associated with each can be detected early and avoided. CONCLUSIONS: For each drug, a series of screening tests prior to use and scheduled testing during use can minimize potential medical complications.

Free sex steroid and sex hormone-binding globulin levels in oligozoospermic men with varicoceles.

OBJECTIVE: To measure free T, free E2, and sex hormone-binding globulin (SHBG) levels in oligozoospermic men with varicoceles. DESIGN: Retrospective study. PATIENTS: Sixty-four infertile patients with varicoceles. SETTING: A university-based tertiary care referral center. INTERVENTIONS: Assessment of seminal cellular characteristics, gonadotropin responses to GnRH, total and free T, and E2 and SHBG levels before and after varicocele ligation. RESULTS: Thirty-eight men had excessive preoperative gonadotropin responses to GnRH. These men had lower than normal levels of free T and higher than normal levels of free E2 and SHBG. Thirty men had improvements in seminal parameters, and sex steroid and SHBG values after surgery. Seven spontaneous pregnancies and three pregnancies through IUI occurred in their partners postoperatively. Twenty-six men had normal preoperative responses to GnRH and normal free T, E2 and SHBG levels. None had postoperative improvements in their semen analyses and no spontaneous pregnancies occurred in their partners. Three pregnancies occurred with IUI. CONCLUSIONS: The men with excessive responses to GnRH had abnormal free sex steroid levels. The majority had improvements in semen analyses after varicocele repair and pregnancies occurred in their partners. The men with normal gonadotropin responces to GnRH had normal free sex steroid levels. Varicocele ligation had no effect on their semen parameters or fertility potential.

Testicular function in hyperthyroidism.

Testicular function was assessed in nine men aged 17 to 35 years and seven men aged 36 to 46 years with Graves' disease. Levels of total testosterone, estradiol, sex hormone binding globulin, luteinizing hormone, and follicle stimulating hormone, and gonadotropin responses to gonadotropin releasing hormone were significantly greater than these levels and responses in age-matched controls. Although the percentage of free testosterone was lower than control values in the hyperthyroid men, calculated levels of free testosterone were not different from normal. Lower than normal percentages of free estradiol values resulted in higher than normal calculated free estradiol levels. As a result, the free testosterone/free estradiol ratio in the men with Graves' disease was lower than normal. Although mean sperm densities in the hyperthyroid men were not different from control values, the percent forward progressive motility of sperm from these men was significantly lower than control values. The hormonal and seminal abnormalities corrected when the patients became euthyroid after radioiodine therapy. The results of this study indicate that hyperthyroid men may have abnormalities in their hypothalamic-pituitary-testicular axes.

11 beta-hydroxyandrostenedione: a marker of adrenal function in hirsutism.

To assess the role of the adrenal glands in the development of hirsutism, levels of 11 beta-hydroxyandrostenedione (11 beta-OHA), 17 alpha-hydroxyprogesterone (17-OHP), dehydroepiandrosterone sulphate (DHEAS), androstenedione (delta 4A), and free and total testosterone (T) were measured in 63 hirsute females and 30 control patients. Six of the hirsute patients had basal levels of 11 beta-OHA and 17-OHP and responses to adrenocorticotropic hormone that were significantly greater than these values in controls and the other hirsute women. These women were designated as having an adrenal source for their hirsutism. Women with polycystic ovarian syndrome and idiopathic hirsutism had normal values of 11 beta-OHA and 17-OHP. Levels of total and free T, DHEAS and delta 4A were significantly higher than control values in all of the hirsute women. This study demonstrates that 11 beta-OHA can be used as a marker to assess the adrenal contribution to hirsutism.

Accuracy of Chlamydia trachomatis antigen detection methods in a low-prevalence population in a primary care setting.

We compared a direct fluorescent-antibody stain (DFA) and an enzyme immunoassay (EIA) with a standard cell culture technique for the detection of Chlamydia trachomatis infection in women in an urban family practice setting. We also evaluated a DFA sample in a commercial laboratory to determine the interlaboratory reliability of this test. There were 268 women in the study; the EIA provided a higher sensitivity (83 versus 50%) and a higher positive predictive value (83 versus 69%) than the DFA test and comparably high specificity (99 versus 98%). Concordance between the two laboratories on the DFA test was not high when data were adjusted for chance agreement (kappa coefficient = 0.64). DFA validity was optimal with an elementary body cutoff of greater than 5, while EIA validity was optimal at the recommended cutoff of 0.1 optical density unit. None of 11 women with negative cultures after treatment had false-positive antigen tests. False-negative results with both tests were associated with low culture inclusion counts but were not strongly associated with the presence or absence of symptoms, menses, pregnancy, or recent antibiotic use. False-positive results with EIA were seen only for three women who had a chief complaint of vaginal discharge. Although the positive predictive value of DFA could be increased in high-prevalence subpopulations, EIA was still more valid in two such groups: teenagers and prenatal patients. These results indicate that EIA might be preferable for low- or moderate-prevalence populations in primary care settings and that a falloff in DFA sensitivity could be explained by lower infection burdens in low-prevalence groups.

Comparison of the nuclear 5 alpha-reduction of testosterone and androstenedione in human prostatic carcinoma and benign prostatic hyperplasia.

The nuclear conversion of testosterone (T) to dihydrotestosterone (DHT) and androstenedione (delta 4A) to androstanedione (5 alpha-Adione) was compared in the separated stromal and epithelial fractions of hyperplastic (n = 6) and malignant (n = 3) prostatic tissues. Assay conditions were linear with respect to time and protein concentration and were optimal for NADPH concentration. The apparent Km values for the stromal enzymes were 0.2 and 0.02 microM for hyperplasia and carcinoma, respectively, using T as substrate. The apparent Km values, using delta 4A as substrate, were 0.03 and 0.02 microM, respectively. Apparent Vmax values for the stromal formation of DHT were 16.5 +/- 5.4 and 1.97 +/- 0.45 pmol/mg protein/30 min incubation, respectively, for the hyperplastic and malignant tissues. The apparent Vmax values for the formation of 5 alpha-Adione were 2.8 +/- 1.3 and 6.5 +/- 1.2 pmol/mg/protein/30 min incubation. The apparent Km values for the epithelial enzyme, for hyperplastic and malignant tissue were 0.04 and 0.04 microM, for T, and 0.05 and 0.03 microM for delta 4A. The respective apparent Vmax values were 4.6 +/- 0.93 and 0.65 +/- 0.07 for DHT and 2.0 +/- 0.86 and 6.4 +/- 0.45 pmol/mg protein/30 min incubation for 5 alpha-Adione. delta 4A was a competitive inhibitor of T 5 alpha-reduction. These results provide further evidence that different rates of 5 alpha-reduction at least partially explain the differences in androgen levels seen in the hyperplastic and the malignant prostate.

Diagnosis of astrovirus gastroenteritis by antigen detection with monoclonal antibodies.

An enzyme-linked immunosorbent assay (ELISA), based on monoclonal antibodies to the astrovirus group antigen, was designed for the detection of astroviruses in stools of patients with gastroenteritis. Compared to immune electron microscopy used as the standard test, the sensitivity of the astrovirus ELISA was 91% (31/34) and the specificity was 96% (54/56). All five of the known astrovirus serotypes could be detected in 16 samples on which serotyping was done. In tests on 155 stools containing other enteric viruses, including adenoviruses, rotaviruses, caliciviruses, Hawaii virus, Snow Mountain virus, and Norwalk virus (30, 20, 70, 24, 4, and 7 samples, respectively), only 3 were positive in the astrovirus ELISA. The combined specificity for all astrovirus immune electron microscopy-negative samples was 98% (206/211). The results demonstrate that the new ELISA provides a sensitive and specific means for the diagnosis of astrovirus gastroenteritis.

Immunological characterization of the Marin County strain of astrovirus.

Marin County virus (MCV) was isolated from a stool suspension and serially propagated in human embryonic kidney cell cultures. MCV particles in stool and cell-propagated virus stocks showed reactivity by immune electron microscopy (IEM) with rabbit antiserum to astrovirus type 5. MCV antigen was also detected in two MCV stool samples by enzyme immunoassay (EIA) with an astrovirus group-specific monoclonal antibody. Acute and convalescent sera from 3 of 3 MCV-infected patients showed seroconversion to cell-propagated MCV by EIA. Immunofluorescence of MCV propagated in cell culture showed positive reactivity with an astrovirus group specific monoclonal antibody and astrovirus type 5 antiserum, with some cross-reactivity with astrovirus type 1. Similar results were obtained with the prototype strain of astrovirus type 5. However, in plaque-reduction assays, both the prototype astrovirus type 5 and MCV were neutralized by type 5 antiserum only. We conclude that MCV can be serially propagated by techniques used for previously described astroviruses and is serotypically an astrovirus type 5.

Plaque quantitation and virus neutralization assays for human astroviruses.

Astroviruses, 28 nm-diameter, RNA-containing viruses which have been implicated in gastroenteritis can be cultivated in cell cultures containing trypsin, but do not show distinguishable cytopathic effects. However, with the 5 known astrovirus serotypes which we have been able to cultivate, 3 (types 1, 2, and 5) formed well-defined plaques in LLCMK2 cell cultures under an agar overlay containing trypsin. A virus neutralization assay based on plaque reduction was applied to these 3 serotypes. It was found that rabbit antisera prepared against individual serotypes neutralized virus type-specifically, and no cross-neutralization titers were obtained with any of the antisera to the 5 astrovirus serotypes. The type-specific neutralization observed agreed with the specificities seen by immunofluorescence (IF), whereas ELISA tests with the same antisera show cross-reactivity among all 5 serotypes. There was no virus neutralization detected with astrovirus monoclonal antibodies which were reactive with 5 serotypes by ELISA and IF. The results we have obtained permit quantitative techniques to be applied to epidemiological and biological studies of the human astroviruses.

Antigenic characterization of cell-cultivated astrovirus serotypes and development of astrovirus-specific monoclonal antibodies.

Cultivation of human astroviruses in human embryonic kidney or LLCMK2 cell cultures was corroborated for four of the five serotypes originally reported (types 1, 2, 4, and 5). By using type-specific rabbit antisera and immunofluorescence of virus-infected cells, we readily distinguished between serotypes of astrovirus; however, these serotypes showed a high degree of cross-reactivity by enzyme-linked immunoassay, a result indicating the presence of a group antigen. We prepared monoclonal antibodies to astrovirus type 2 antigen and selected them on the basis of group antigen reactivity. The antibodies were reactive with the four astrovirus serotypes that we could cultivate, as well as with the Marin County strain of astrovirus. A previously reported cell-cultivated astrovirus type 3 also reacted with the monoclonal antibodies. These monoclonal antibodies, and the finding of group reactivity among the human astroviruses, should facilitate studies on the importance of these viruses as agents of viral gastroenteritis.

The endocrinology of varicoceles.

There is good evidence of an associated abnormality in testicular hormone production and spermatogenesis in some men with varicoceles. This abnormality can be demonstrated with dynamic tests of the hypothalamic-pituitary-testicular axis and by measuring seminal plasma androgen levels. A high proportion of oligozoospermic men who have abnormal hormone profiles will respond favorably to correction of their varicosities. Several oligozoospermic men with varicoceles have normal hormonal profiles. To date, in our unit, none of these men has had an improvement in seminal characteristics after varicocelectomy. This result would suggest that these men have incidental varicoceles. It is not clear what the testicular defect is leading to abnormal spermatogenesis in these men. Clearly, more studies are required in this group of men and in the men with sperm densities greater than 30 X 10(6)/ml, the majority of whom have normal responses to GnRH infusion. More information is needed regarding the intratesticular control of hormone production and spermatogenesis. As our knowledge of the paracrine system within the testis increases, so should our understanding of the mechanisms involved in the association of varicoceles and infertility.

The prolactin response of males to a standard MVO2 treadmill test.

The concentration of serum prolactin in response to a standard MVO2 treadmill stress test to self-perceived exhaustion was investigated in 19 normal healthy males. The prolactin concentration remained stable for an interval of approximately 20 minutes from the beginning of exercise. Peak prolactin levels, observed after the subjects had stopped exercising, indicated a mean 2.6-fold increase over pre-exercise levels. The concentration of prolactin did not increase before an exercise intensity reflecting a VO2 of 40 ml/kg/min had been reached. There was no relationship between the MVO2 of the 19 male subjects and their prolactin increment in response to exercise.

Comparison of nuclear 5 alpha-reductase activities in the stromal and epithelial fractions of human prostatic tissue.

The nuclear conversion of testosterone (T) to dihydrotestosterone (DHT) was compared in the separated stromal and epithelial fractions of hyperplastic (n = 20), malignant (n = 5) and normal (n = 1) prostatic tissues. Standard assay conditions were: 1 microM testosterone, plus 4-6 X 10(5) DPM [3H]T, 1.0 mM NADPH, 2.0 mM EDTA and 0.5-1.0 mg nuclear protein in a total volume of 1.1 ml HEPES buffer, pH 7.4 (stroma) or MES buffer, pH 6.5 (epithelium). The apparent Km values for the stromal enzyme were 0.2, 0.2 and 0.3 microM, respectively, for the enzymes in hyperplastic, malignant and normal tissues. The Vmax values were 26 +/- 4.2, 2.8 +/- 0.6 and 4.1 pmol/mg protein/30 min incubation, respectively, for these same tissues. The apparent Km values for the epithelial enzymes, from the same tissues, were 0.03, 0.07 and 0.08 microM. The Vmax values for the epithelial enzymes were 4.8 +/- 1.2, 0.69 +/- 0.08 and 1.1 pmol/mg protein/30 min incubation. The pH optimum for the stromal enzyme lay between pH 6.5 and 7.5, whereas the pH optimum for the epithelial enzyme lay between 5.5 and 6.5. Enzymatic activity in both fractions revealed a biphasic response to zinc. In the absence of EDTA, microM quantities of zinc enhanced enzymatic activity while mM quantities inhibited this activity. These results would suggest that differences in the conversion of T to DHT help to explain, at least in part, the higher DHT levels seen in hyperplastic tissue and the higher T levels seen in the malignant prostate.

Hormonal parameters in incidental varicoceles and those causing infertility.

The gonadotropin responses to a 4-hour infusion of gonadotropin-releasing hormone (GnRH), the prolactin (PRL) responses to a bolus injection of thyrotropin-releasing hormone (TRH), and seminal plasma dihydrotestosterone (DHT) levels were assessed before and 6 to 12 months after varicocelectomy was performed in 56 infertile men with varicoceles and sperm densities less than 30 X 10(6)/ml. The men were divided into four groups, determined by their sperm densities and hormonal parameters. Groups I (18 men) and II (12 men) had sperm densities less than 10 X 10(6)/ml, and groups III (16 men) and IV (10 men) had sperm densities of 11 to 30 X 10(6)/ml. The men from groups I and III had excessive preoperative gonadotropin and PRL responses, and lower-than-normal seminal plasma DHT levels. The men in groups II and IV had normal hormonal values. After operation, 12 of the men from group I and 11 from group II had improvements in seminal and hormonal parameters. The other men in these two groups and all of the men in groups II and IV had no changes in seminal and hormonal parameters after operation. This study indicates that an assessment of these hormonal parameters may be useful in predicting which men with varicoceles are likely to have an improvement in sperm density after varicocele repair.

Hormonal parameters of men with varicoceles before and after varicocelectomy.

The gonadotropin responses to a 4-hour infusion of gonadotropin-releasing hormone (GnRH) and seminal plasma dihydrotestosterone (DHT) and testosterone levels were assessed before and 6 to 12 months after varicocelectomy in 22 men with varicoceles. Twelve men were severely oligozoospermic (sperm densities less than 10 X 10(6)/ml), whereas 10 men had sperm densities between 11 and 30 X 10(6)/ml. Each man had excessive gonadotropin responses to GnRH and lower than normal seminal plasma DHT levels preoperatively. Eight of the 12 severely oligozoospermic men and 6 of the other 10 men had postoperative improvements in sperm density. These men (responders) had normalization of gonadotropin response and seminal plasma DHT levels. The nonresponders had identical hormonal parameters before and after surgery. These results indicate that the pantesticular defect in hormonal synthesis and spermatogenesis, seen in some men with varicoceles, can be reversible.

Comparison of 3 alpha-hydroxysteroid dehydrogenase activities in the microsomal fractions of hyperplastic, malignant and normal human prostatic tissues.

The conversion of dihydrotestosterone (DHT) to 3 alpha-androstanediol (3 alpha-adiol) was studied using the microsomal fractions of 15 hyperplastic, 5 malignant and 6 normal human prostatis tissues. Standard assay conditions were: 0.2 microM DHT, 1.0 mM NADPH, 1.0 mM NADH, 2.0 mM EDTA and the microsomal fractions equivalent to 200 mg of prostatic tissue, in 0.1 M MES buffer, pH 6.5. Under the conditions of this assay, the back-conversion of 3 alpha-adiol to DHT or the conversion of DHT to androstanediol were negligible. Optimum enzyme activity was achieved under standard assay conditions. In the absence of EDTA: enzyme activity was 65% of the standard assay; activity was diminished further by 2 mM Ca2+ and virtually eliminated by 2 mM Mg2+ or 2 microM Zn2+. Activity in the absence of either NADPH or NADH was only 50% of the activities seen in the presence of both cofactors. The pH optimum of the enzyme was between 6.0 and 6.5. The apparent Km values of the enzymes in hyperplastic, malignant and normal tissues were 0.03, 0.02 and 0.03 microM, respectively. The Vmax values for these tissues were 6.0 +/- 2.1, 1.6 +/- 0.5 and 14.0 +/- 3.0 pmol/mg protein/20 min incubation, respectively. The results of these experiments offer further explanation for the differences in DHT and 3 alpha-adiol levels seen in the 3 prostatic tissues.