Ethnic differences in osteocalcin gamma-carboxylation, plasma phylloquinone (vitamin K1) and apolipoprotein E genotype.

OBJECTIVE: To investigate plasma osteocalcin gamma-carboxylation and its relationship to plasma phylloquinone concentration and apolipoprotein E (apoE) genotype in women from three ethnic groups with differing osteoporotic fracture risk. DESIGN AND SUBJECTS: Fasted blood samples were collected from postmenopausal Gambian (n=50), British (n=31) and Chinese women (n=23), and 11 premenopausal women in each group from three cross-sectional studies. RESULTS: After adjustment for total osteocalcin, plasma undercarboxylated osteocalcin (adjusted ucOC) was lowest in Chinese and highest in British women postmenopause (British vs Chinese 103% higher, P<0.0001; Gambian vs Chinese 66% higher, P<0.01). No differences were observed premenopause. Within each ethnic group, adjusted ucOC was similar pre- and postmenopause. Postmenopause, plasma phylloquinone was higher in Chinese women (1.0 ng/ml) than in British (0.31 ng/ml) and Gambian women (0.36 ng/ml) (P<0.0001). Premenopause, plasma phylloquinone was higher in Gambian and Chinese women (0.6 ng/ml) than in British women (0.3 ng/ml; P=0.01). Plasma phylloquinone and adjusted ucOC were inversely related in postmenopausal British women (R2=32.4%; P=0.0008). ApoE4 frequency was Gambian 32.6%, British 13.8% and Chinese 6%. A lower adjusted ucOC was associated with apoE2 genotype in British and Chinese women. Ethnic differences in adjusted ucOC persisted after adjustment for phylloquinone and apoE genotype. CONCLUSION: These preliminary data indicate suboptimal vitamin K status in postmenopausal British compared to Chinese and Gambian women. Ethnic differences in apoE genotype may also influence osteocalcin gamma-carboxylation status. The study highlights the need for larger epidemiological investigations of ethnic differences in vitamin K status and the possible implications to bone health.

Age- and gender-related differences in bone mineral status and biochemical markers of bone metabolism in Northern Chinese men and women.

The aim of this study was to provide insight into the bone mineral status and biochemical markers of bone metabolism in a Chinese population from Shenyang, in the north of China, where hip fracture incidence is low. A total of 194 healthy men and women, aged 25-35 years and 65-75 years, were studied. Bone mineral density (BMD) at the lumbar spine (LS) and femoral neck (FN) was measured using dual-energy X-ray absorptiometry. Fasting blood and 24 h urine samples were collected for bone alkaline phosphatase (bAP), osteocalcin, calcium, phosphate, and free deoxypyridinoline (Dpd). Both older women and men had lower BMD compared with younger women and men by 27.2 +/- 3.0% (mean +/- SE) and 9.8 +/- 3.0% at the LS and 22.0 +/- 3.4% and 12.8 +/- 3.4% at the FN, respectively, after adjusting for bone and body size (p < 0.01). BMD at the two sites was lower in older women than in older men by 10.7 +/- 4.1% and 10.2 +/- 4.2%, respectively, after size correction (p < 0.05). Plasma bAP, osteocalcin, calcium, and phosphate concentrations were higher in older women than younger women by 69.3 +/- 9.7%, 77.2 +/- 11.1%, 7.5 +/- 2.3%, and 8.0 +/- 3.8%, respectively, and older men by 67.6 +/- 11.1%, 72.1 +/- 11.0%, 7.7 +/- 2.3%, and 23.8 +/- 3.8%, respectively (p < 0.01). However, plasma osteocalcin, calcium, and phosphate concentrations were lower in older men compared with their younger counterparts by 35.6 +/- 11.0%, 8.7 +/- 2.3%, and 14.1 +/- 3.8%, respectively (p < 0.05). Urinary calcium and phosphate output were lower in older men compared with younger men by 48.0 plus minus 10.3% and 27.6 +/- 6.9%, respectively (p < 0.01), whereas there were no differences between older and younger women. No differences in Dpd between older and younger groups were found. This study demonstrates that bone mineral status is lower in older people in Shenyang, as has been shown in populations elsewhere. The pronounced low bone mineral status in older women may be associated with increased bone turnover, which was not observed in older men.

Vitamin D status and parathyroid hormone concentrations in Chinese women and men from north-east of the People's Republic of China.

STUDY OBJECTIVE: To evaluate vitamin D status of young and old women and men living in Shenyang, north-east People's Republic of China in early spring and to explore the relationship between vitamin D metabolites and parathyroid hormone (PTH) in this population. DESIGN: Cross-sectional study. SETTING: Shenyang, north-east China. SUBJECTS: 194 healthy volunteers: 48 young women and 48 young men aged 25-35 y, and 48 old women and 50 old men aged 65-75 y. RESULTS: Fasting blood samples were used to measure plasma 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)2D) and PTH using radioimmunoassays. The proportion of subjects who could be regarded as vitamin D deficient (<25 nmol/l) was 48%, 29%, 15% and 13% for old men, young men, old women and young women, respectively. There was no association between plasma 1,25(OH)2D and 25(OH)D concentrations. PTH concentrations were elevated in both old women and men compared with young subjects (P<0.01). A negative association between PTH and 25(OH)D was only found in old women (P<0. 001), but not in old men, nor in young subjects. CONCLUSIONS: Vitamin D status was poor in this population in early spring, especially in men. There was no clear evidence to show that the secretion of PTH and the conversion of 1,25(OH)2D were affected by the low 25(OH)D concentration. SPONSORSHIP: Partly supported by the Sandoz Foundation for Gerontological Research and the Nestlé Foundation, Switzerland, and Medical Research Council, UK. European Journal of Clinical Nutrition (2000) 54, 68-72

Effect of calcium supplementation on bone mineral accretion in gambian children accustomed to a low-calcium diet.

BACKGROUND: Rural Gambian children have poor growth, delayed puberty, a low bone mineral content, and a low calcium intake. OBJECTIVE: We investigated the effect of a calcium supplement on bone mineral accretion in rural Gambian children. DESIGN: A randomized, double-blind, placebo-controlled study was conducted in 160 children (80 boys, 80 girls) aged 8.3-11.9 y. Bone mineral content (BMC), bone mineral density (BMD), and BMC adjusted for bone width, body weight, and height (size-adjusted BMC) were measured at the midshaft and distal radius. Each child received either 1000 mg Ca/d (as calcium carbonate) or a placebo 5 d/wk for 12 mo. Supplementation increased calcium intake from 342 to 1056 mg/d (8.6 to 26.4 mmol/d). RESULTS: Calcium supplementation resulted in a higher BMC, BMD, and size-adjusted BMC (&xmacr; difference +/- SE): midshaft radius-BMC (3.0 +/- 1.4%; P = 0.034), BMD (4.5 +/- 0.9%; P

An investigation of ethnic differences in bone mineral, hip axis length, calcium metabolism and bone turnover between West African and Caucasian adults living in the United Kingdom.

The aim of the study was to investigate factors relating to calcium and bone metabolism which might explain the low incidence of osteoporotic fracture among Africans. Adult bone mineral status, hip axis length and biochemical indices were investigated in 20 Caucasians (10 male, 10 female) and 19 Gambians (12 male, 7 female) living in the UK. Bone mineral content (BMC), bone mineral density (BMD) and BMC adjusted for bone area, body weight and height (size-adjusted BMC) were measured for the whole-body, lumbar spine, femoral neck, trochanter, radius shaft and radius wrist using dual-energy X-ray absorptiometry. There were no significant differences in whole body or regional BMC; values tended to be lower in the Gambians. Gambian men had higher size-adjusted BMC at the femoral neck (Gambian-British = 21%, 95% CI = 6 to 36%, p < 0.01), associated with a smaller bone area (Gambian-British = -11%, 95% CI = -20 to -2%, p = 0.02). BMD was affected similarly. No other significant differences in BMD or size-adjusted BMC were observed. Gambians had shorter hip axis length (Gambian British, after accounting for sex, = -5%, 95% CI = -9 to -1%, p = 0.02). There were no significant differences in bone turnover (osteocalcin, bone isoenzyme of alkaline phosphatase, urinary deoxypyridinoline) or calciotropic hormone levels (parathyroid hormone, 1,25-dihydroxyvitamin D, calcitonin). Gambian men had lower 25-hydroxyvitamin D concentrations (Gambian = 26.3 SD 12.0 nmol/L, British = 55.5 SD 13.9 nmol/L, p < 0.0001), a difference not seen among the women. Gambian men and women excreted significantly less phosphate and potassium than British subjects by 30-60%; urinary calcium and sodium excretion were similar in the two groups. This study revealed few ethnic differences that could account for the disparity in osteoporotic fracture rates between Africans and Caucasians, with the possible exception of anatomical differences in the hip.

Biochemical markers of calcium and bone metabolism during 18 months of lactation in Gambian women accustomed to a low calcium intake and in those consuming a calcium supplement.

The effect of 18 months of lactation on indexes of calcium and bone metabolism was studied in 60 Gambian women accustomed to a very low calcium intake. Half the women consumed a calcium supplement from 10 days postpartum for 52 weeks (supplement, 714 mg Ca/day; total Ca intake, 992 +/- 114 mg/day), and half consumed placebo (total Ca intake, 288 +/- 128 mg/day). Fasting blood and 24-h urine samples were collected at 1.5, 13, 52, and 78 weeks of lactation and analyzed for calciotropic hormones (intact PTH, 1,25-dihydroxyvitamin D, and calcitonin), bone turnover markers (osteocalcin, bone alkaline phosphatase, and urinary deoxypyridinoline), and plasma minerals (calcium and phosphate). The first months of lactation were associated with increased bone turnover and plasma phosphate, and decreased PTH and 1,25-dihydroxyvitamin D. These effects diminished by 52 weeks, although breast milk volumes remained high. The Gambians had higher PTH, 1,25-dihydroxyvitamin D, and bone formation than British women with a greater customary calcium intake. None of the biochemical indexes was affected by calcium supplementation, with the possible exception of bone alkaline phosphatase (-29% at 52 weeks; P = 0.015). These data demonstrate that lactation-associated changes in calcium and bone metabolism are physiological and are independent of dietary calcium supply in women with very low calcium intakes.

Vitamin D status does not influence the breast-milk calcium concentration of lactating mothers accustomed to a low calcium intake.

Plasma 25-hydroxy-vitamin D and breast-milk calcium concentration were measured at 3 months of lactation in 60 Gambian mothers accustomed to a low calcium diet, of whom 30 were consuming a calcium supplement and 30 were receiving a placebo, and in 48 British mothers. The plasma 25-hydroxy-vitamin D concentration of the Gambian women was not affected by either calcium supplementation (supplemented, 64.4 +/- 2.5 nmol l(-1); placebo, 64.9 +/- 3.5 nmol l(-1); mean +/- SE) or season. The British average was lower (53.9 +/- 3.0 nmol l(-1), p = 0.004), owing to marked seasonal effects. The breast-milk calcium concentration was lower in The Gambia (supplemented, 5.38 +/- 0.13 mmol l(-1); placebo, 5.10 +/- 0.13 mmol l(-1); British, 6.93 +/- 0.15 mmol l(-1), p < 0.0001). There was no relationship between plasma 25-hydroxy-vitamin D and breast-milk calcium concentration in any group. There was no trend towards lower breast-milk calcium concentration in women with vitamin D status towards the bottom of the normal range or in British women during the winter. This study provides no support for the hypothesis that breast-milk calcium concentration is influenced by vitamin D status or that lactating women with a low calcium intake are at particular risk of vitamin D deficiency.

The effect of long-term calcium supplementation on indices of iron, zinc and magnesium status in lactating Gambian women.

The effect of long-term supplementation with CaCO3 on indices of Fe, Zn and Mg status was investigated in a randomized, double-blind intervention study of sixty lactating Gambian women. The supplement contained 1000 mg Ca and was consumed between meals 5 d/week, for 1 year starting 1.5 weeks postpartum. Compliance was 100%. Plasma ferritin concentration, plasma Zn concentration and urinary Mg output were measured before, during and after supplementation at 1.5, 13, 52 and 78 weeks postpartum. No significant differences in mineral status were observed at any time between women in the supplement and placebo groups. Analysis of the longitudinal data series showed that plasma ferritin and Mg excretion were characteristic of the individual (P < 0.001). Within individuals, ferritin concentration was higher at 1.5 weeks postpartum than later in lactation (P = 0.002). Plasma Zn concentration was lower at 1.5 weeks postpartum than at other times (P < 0.001), an effect which disappeared after albumin correction. Low plasma concentrations of ferritin and Zn indicated that the Gambian women were at high risk of Fe and Zn deficiency. Measurements of alpha 1-antichymotrypsin suggested that the results were not confounded by acute-phase responses. The results of the present study indicate that 1000 mg Ca as CaCO3 given between meals does not deleteriously affect plasma ferritin and Zn concentrations or urinary Mg excretion in women who are at risk of Fe and Zn deficiency.

PIP: During March 1990-March 1991, 60 lactating mothers were recruited into a randomized, placebo-controlled trial designed to examine the effect of calcium (Ca) supplementation on plasma zinc (Zn) and ferritin (Fe) concentrations and on magnesium (Mg) excretion during and after Ca supplementation. The women lived in Keneba and Manduar villages in rural Gambia. They consumed 1000 mg Ca or the placebo (2 tablets of dextrose) between meals 5 days/week for 12 months beginning 1-5 weeks postpartum. All women complied. At no time were there significant differences in the indices used to determine Zn, Fe, and Mg status between lactating women on Ca supplements and those receiving the placebo. In fact, the mean differences were less than 10% of the total value. Many women (33-50%), regardless of supplementation group, had a plasma Fe concentration lower than 12 mcg/l, indicating depleted Fe stores. Many women also had low plasma Zn levels. Within individuals, plasma Zn concentrations were 15% lower at day 9 than later in lactation (p 0.001), while plasma Fe levels were 10% higher (p = 0.002). Plasma Zn levels were associated with plasma albumin levels (p 0.001). When adjusted for albumin, the effect of lactation on Zn disappeared. When compared with British women, Gambian women had a lower plasma Zn concentration (p 0.001). Within individuals and after adjustment for lactation stage and for albumin, plasma Zn levels varied between seasons (i.e., hot season values higher than other seasons) (p = 0.004). Women were more likely to excrete Mg during the hot season (p 0.001). These findings indicate that ingestion of 1000 mg Ca between meals has no adverse effect on plasma Fe and Zn levels or urinary Mg excretion in women at risk of Zn and Fe deficiency.

Early increase in plasma parathyroid hormone levels following liver transplantation.

BACKGROUND/AIMS: The pathogenesis of post-transplantation bone loss is poorly understood, although glucocorticoid therapy is believed to play an important role. In the present study we have measured plasma parathyroid hormone concentrations in the first few months after orthotopic liver transplantation, in order to examine the potential contribution of hyperparathyroidism to bone disease. PATIENTS AND METHODS: Twenty-seven patients aged 32-54 years, 12 male, undergoing liver transplantation were studied prospectively before and for 3 months after operation. Plasma parathyroid hormone and serum 25-hydroxyvitamin D concentrations were measured by radioimmunoassay. RESULTS: Plasma parathyroid hormone levels were normal in all but two patients prior to transplantation. There was a highly significant increase in plasma parathyroid hormone concentrations at 1 and 2 months (p < 0.0005 and 0.001, respectively, versus baseline); by 3 months, values were close to those obtained preoperatively. Serum 25-hydroxyvitamin D concentrations showed no significant change over the study period. However, 74% of the patients had subnormal values at baseline. CONCLUSIONS: An early and transient increase in plasma parathyroid hormone after liver transplantation may be responsible for the high rates of bone loss which occur during the first few post-operative months. Prevention of post-transplantation bone disease is most likely to be achieved by peri-operative intervention with an anti-resorptive agent.

Effect of calcium supplements and stage of lactation on the calcium absorption efficiency of lactating women accustomed to low calcium intakes.

The effect of calcium intake on the calcium absorption efficiency from 100 mL cow milk was measured in lactating Gambian mothers habituated to a low-calcium diet [mean intake 7.08 mmol (283 mg)/d], and compared with UK lactating mothers consuming high-calcium diets [mean intake 29.2 mmol (1168 mg)/d] by using a double stable-isotope technique (oral 44Ca and intravenous 42Ca). In a double-blind trial starting 9 d postpartum, Gambian mothers were given a calcium supplement [17.85 mmol (714 mg)/d] or placebo for 12 mo. At 3 and 12 mo postpartum, mean (+/- SEM) calcium absorption from isotopically enriched milk was 52.3 +/- 3.1% (n = 25) and 47.2 +/- 4.8% (n = 24) in the unsupplemented Gambian mothers and 48.8 +/- 2.8% (n = 28) and 42.9 +/- 3.7% (n = 24) in the supplemented mothers, respectively. There was no effect of supplementation or stage of lactation on the efficiency of calcium absorption. At 3 mo postpartum the UK mothers absorbed 32.2 +/- 3.8% of the isotopically enriched calcium added to milk, which was significantly less than that of the Gambian mothers (P < 0.01).

Calcium requirements of lactating Gambian mothers: effects of a calcium supplement on breast-milk calcium concentration, maternal bone mineral content, and urinary calcium excretion.

The calcium requirement for prolonged lactation was investigated in a randomized supplementation study of Gambian mothers consuming a low-calcium diet (7.1 mmol/d, or 283 mg/d). Sixty women were studied from 10 d to 78 wk of lactation, receiving calcium or placebo for the first 12 mo. The supplement increased average calcium intake by 17.9 mmol/d (714 mg/d). Supplementation had no effect on breast-milk calcium concentration or on maternal bone mineral content. Urinary calcium output was higher in supplemented than in unsupplemented mothers by 1.18 mmol/d (47 mg/d), P < or = 0.005. Longitudinal changes in urinary calcium output and bone mineral content made a substantial contribution to calcium requirements for lactation. This study suggests that, in women with low calcium intakes, there is no direct benefit from increasing calcium intake during lactation, and that physiological mechanisms operate to furnish calcium for breast-milk production.

Osteoporosis in severe congenital neutropenia treated with granulocyte colony-stimulating factor.

Recombinant human granulocyte colony-stimulating factor (G-CSF) has substantially improved life expectancy for children with severe congenital neutropenia (SCN). Severe osteoporosis, reported in this population, may relate to the disease process, or be a therapeutic side-effect. This report details bone loss, quantitated absorptiometrically and histomorphometrically, in a child with SCN and vertebral collapse, and the positive response to anabolic steroid and bisphosphonate therapy.

Raised urinary secretory IgA in chronic diarrhoea.

Secretory IgA outputs in urine have been measured in 24 malnourished Gambian children who had been admitted to hospital with chronic diarrhoea and in 43 children from a rural Gambian village. Village children of poor nutritional state (less than or equal to 74% weight for age compared with the National Center for Health Statistics reference curve) had secretory IgA outputs that were only one third of those of better nourished individuals. In contrast, the patients with chronic diarrhoea had secretory IgA outputs that were significantly raised compared with village children, regardless of nutritional state. These results demonstrate that secretory IgA production in the urinary tract can be stimulated by intestinal disease, suggesting that malnourished children are able to mount a response to mucosal infection and supporting the hypothesis of a common secretory immune system.

Breast-milk IgA and lactoferrin survival in the gastrointestinal tract--a study in rural Gambian children.

The survival of breast-milk secretory-IgA and lactoferrin has been investigated in 23 Gambian children aged 1.5, 3 and 17 months. Endogenous excretion of these immune proteins was measured in 7 weaned 34-month-old children. Defaecation rate was the prime determinant of faecal secretory-IgA and lactoferrin outputs, indicating that partial degradation occurs in the large intestine. Calculations showed that at least 30% of IgA and 2% of lactoferrin ingested from breast-milk must survive in the small intestine. Variations in faecal immune protein outputs were related to differences in intake and defaecation rate and were not affected by age or solid food consumption. The raised faecal outputs of 5 children with diarrhoea were a consequence of their high stool frequencies. IgA disappearance in the large intestine proceeded twice as fast in Gambian breast-fed children as in comparable Cambridge infants, suggesting that differences in gut flora may influence IgA survival. Thus breast-feeding, irrespective of age or additional food, can deliver significant quantities of these antimicrobial proteins to the small intestine but differences in defaecation rate and gut flora may affect their protective potential in the large intestine.

Effect of warm or cold exposure on GDP binding and uncoupling protein in rat brown fat.

The effects of acute and chronic exposure to different environmental temperatures on the total tissue cytochrome oxidase activity, level of mitochondrial GDP binding, and specific mitochondrial concentration of uncoupling protein have been investigated in rat brown adipose tissue, a radioimmunoassay being used to measure uncoupling protein. Acclimation at different temperatures for 3 wk produced parallel changes in GDP binding, the concentration of uncoupling protein, and the activity of cytochrome oxidase, each parameter rising with decreasing temperature between thermoneutrality (29 degrees C) and 4 degrees C. Acute exposure of warm-acclimated (29 degrees C) rats to the cold (4 degrees C) led to a rapid increase in GDP binding without any alteration in the amount of uncoupling protein. The increase in binding was accompanied by an increase in the rate of acetate-induced swelling of the mitochondria. The concentration of uncoupling protein in warm-acclimated rats was significantly raised only after 48 h exposure to cold. When cold-acclimated rats were exposed acutely to the warm, there was a rapid decrease in GDP binding without any alteration in the amount of uncoupling protein. It is concluded that after alterations in environmental temperature the concentration of uncoupling protein in brown adipose tissue mitochondria changes much more slowly than GDP binding and that binding can therefore be dissociated from the amount of the protein.

Decreased brown adipose tissue thermogenic activity following a reduction in brain serotonin by intraventricular p-chlorophenylalanine.

The effects of reducing brain serotonin (5-HT) levels by means of intracerebral-ventricular injections of the tryptophan antagonist p-chlorophenylalanine (PCPA) were investigated in male rats. Six days after the operation, PCPA-treated rats, either fed ad libitum or pair-fed to the food intake of control rats, showed decreased thermogenic activity and capacity in their interscapular brown adipose tissue (BAT) and also increased fat storage in their white adipose tissue (WAT). These results indicate that serotonergic synapses might play a regulatory role in the sympathetic control of BAT thermogenesis and in the rate of WAT deposition (by an as yet unidentified mechanism), in addition to their well established role in controlling food intake.

Measurement by radioimmunoassay of the mitochondrial uncoupling protein from brown adipose tissue of obese (ob/ob) mice and Zucker (fa/fa) rats at different ages.

The concentration of the 'uncoupling protein' in brown adipose tissue mitochondria has been measured in lean and obese (ob/ob) mice and Zucker (fa/fa) rats at different ages using a specific radioimmunoassay. During the suckling period the concentration of the protein was similar in normal and mutant animals of both types, despite the decrease in mitochondrial GDP binding observed in the obese. The concentration of uncoupling protein was, however, decreased in adult ob/ob mice and adult Zucker rats compared with their respective lean siblings, in parallel with the decrease in GDP binding. It is concluded that there is a 'masked', or inactive, form of uncoupling protein in young ob/ob mice and fa/fa rats.

Effect of acclimation temperature on the concentration of the mitochondrial 'uncoupling' protein measured by radioimmunoassay in mouse brown adipose tissue.

The effect of acclimation temperature on the concentration of the mitochondrial 'uncoupling' protein (Mr 32000) from brown adipose tissue of mice has been investigated. The uncoupling protein was measured by a specific radioimmunoassay. Between 33 degrees C (thermoneutrality) and -2 degrees C there was a progressive increase with decreasing environmental temperature in the amount of uncoupling protein. For mice at -2 degrees C the mitochondrial concentration of the protein was 9-times higher than at 33 degrees C, while the total amount of the protein in interscapular brown adipose tissue was estimated to be nearly 80-times greater at -2 degrees C compared to 33 degrees C.