SummaryCell surface proteoglycans play an important part in the functional and metabolic behaviour of leucocytes. We studied the expression of cell surface proteoglycans in human monocytes, in monocyte-derived immature and mature dendritic cells and in macrophages by metabolic labelling with [

Background: Regulatory mechanisms of metabolic homeostasis undergo important alterations during ageing. The age-related changes become often evident only during stimulation of basic functions that occurs, e.g. during fasting and refeeding which represent natural challenge to energy metabolism. Objective: To determine the effect of short-term fasting and subsequent refeeding on serum levels of key hormones and metabolites in young adult 5- and 24-month-old male Wistar rats. Methods: Control rats were fed ad libitum. Animals were fasted for 48 h or fasted and refed for 24 h. Metabolite serum concentrations were measured by standard methods. Leptin and insulin were determined by rat-specific RIA, and adiponectin serum levels by mouse/rat–specific ELISA. Results: (1) Control serum levels of key metabolites and hormones were similar in both age groups except for increased triglycerides (TG) in old fed rats. (2) Fasting caused a significant decrease of leptin, insulin, glucose, and TG serum levels in both age groups, and an increase of free fatty acids (FFA) concentration, however, only in young animals. (3) Upon refeeding serum glucose, TG and insulin reversed to control levels in both age groups, however, FFA concentration decreased to control values only in young rats. (4) In contrast to young animals, refeeding of old rats did not increase serum leptin concentration to control level. (5) Neither fasting nor refeeding changed adiponectin serum levels in both age groups. Conclusion: Aging suppresses leptin secretion and metabolism of FFA during refeeding that follows short-term starvation. In old rats serum levels of FFA are refractive to the alterations induced by fasting/refeeding in young ones.

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Background: On the basis that (1) multiple interactions exist between the hormonal and immune systems, and (2) aging is accompanied by changes in thyroid hormone metabolism and responsiveness, we postulate that thyroid hormones may be involved in the observed decrease in natural killer (NK) activity in a population of apparently healthy elderly subjects. The purpose of the study is to compare NK cytotoxic activity and serum concentrations of TSH and thyroid hormones in healthy old and young people, and to assess in vitro the effects of triiodothyronine (T₃) on NK activity. Materials and Methods: Sixteen of the 47 healthy old people (mean age 64 ± 5.2) were classified as optimally healthy, and the remainder as ‘almost healthy’ (according to the criteria of the Senieur protocol) [Ligthart et al., Mech Ageing Dev 1984;28:47–55]; the mean age of the healthy young people was 23.3 ± 2.3 years. NK cytotoxic activity of peripheral blood mononuclear cells was assessed using ⁵¹Cr release from K562 target cells. The cutoff level for defining low and high NK responses was set at a value of 20%. Serum concentrations of TSH, total thyroxine (T₄) and total triiodothyronine (T₃) were measured by radioimmunoassay. Results: NK activity in the ‘optimally healthy’ elderly was high (mean 41 ± 12%, SE), whereas ‘almost healthy’ subjects showed low NK activity (mean 6 ± 5%). Serum T₄ and TSH levels, but not T₃ concentrations were similar in both the young and old. We observed a significant correlation (r = 0.53, n = 21, p < 0.05) between the serum total T₃ level and the NK activity in the elderly individuals. Under in vitro conditions exogenous T₃ significantly increased NK activity in the elderly subjects who had serum T₃ values at the lower end of the reference range. However, no effect of T₃ on NK activity was observed in peripheral blood mononuclear cells obtained from either old or young individuals who had serum T₃ levels at the midpoint of the range. Conclusion: Decreased serum concentrations of total T₃ may contribute to low NK activity in the ‘almost healthy’ subgroup of the elderly.