Is there a link between insulin resistance and chronic kidney disease in men with treated hypertension? Analysis of 5-year data

BACKGROUND/AIMS

Hypertension, chronic kidney disease (CKD) and cardiovascular disease (CVD) have reached epidemic proportions globally. Patients with CKD are at increased risk of CVD and yet conventional factors have yet to be linked with the risk associated with patients with CKD. The aim of this research was to establish whether there is a link between insulin resistance (IR) and estimated glomerular filtration rate (eGFR), and assess whether insulin-resistant subjects experience a more rapid deterioration in eGFR.

METHODS

IR was determined using HOMA-IR (homeostasis model assessment for IR) in normoglycaemic, male subjects with treated hypertension and correlated with clinical variables over a period of 5 years.

RESULTS

106 subjects were assigned to three groups according to insulin sensitivity. Patients with IR had a higher body mass index, fasting glucose, triglyceride and lower HDL cholesterol. Half of the insulin-resistant patients developed an impaired fasting glucose by 1 year and 14% were being treated for type 2 diabetes mellitus by 5 years. Baseline and 5-year data revealed that there was no link between IR and eGFR, which deteriorated equally in all groups.

CONCLUSION

We established that both CKD and IR are common and that the majority of subjects with IR developed impaired fasting glucose or type 2 diabetes mellitus in only 5 years. Although eGFR deteriorated in all groups, no link was found between eGFR and IR.

Occult donor malignancy in pancreas transplantation

Tumor of the pancreas allograft is extremely rare. We report a case of an occult donor malignant undifferentiated tumor arising in a pancreas allograft. A 42-year-old female with Type 1 diabetes received a macroscopically normal pancreas allograft. The donor was a 22-year-old male who died of spontaneous intracerebral hemorrhage. She underwent transplant pancreatectomy, the histology of the pancreas allograft demonstrated a tumor measuring 5 mm in diameter, and a diagnosis of malignant undifferentiated tumor was made. In a different transplant center, the recipient of the left kidney transplant from the same donor had a nephrectomy, and the recipient of the liver transplant died of metastatic disease. Microscopic examination of the liver and kidney allografts subsequently revealed histological features identical to the pancreas tumor. Tumor transmission in transplantation may occur from an organ that contains metastatic cells or, less commonly, from the transmission of an unrecognized or occult primary tumor. A report from the United Network for Organs Sharing transplant data 1997-2002 is illustrated and discussed. This case illustrates the difficulties associated with identifying donors with occult primary tumor or metastases.

Insulin resistance in men with treated hypertension at increased risk for cardiovascular disease: results of a 3-year study

BACKGROUND

Insulin resistance is an independent risk factor for cardiovascular disease. The aim of this research was to establish the frequency of insulin resistance in a normoglycemic, hypertensive, male population to determine whether insulin resistance could be predicted by assessment of conventional risk factors and to assess the rate of deterioration.

METHODS

Insulin resistance was calculated in hypertensive patients and healthy control subjects using a homeostasis model assessment for insulin resistance (HOMA-IR) and was correlated with routinely measured clinical variables.

RESULTS

A total of 106 patients and 18 healthy control subjects were recruited. The healthy control subjects were similar to the patients in age and body mass index (BMI) but had a lower fasting glucose, insulin, and HOMA-IR. Of the patients, 36 were insulin sensitive (IS, HOMA-IR <1.5) and 21 were insulin resistant (IR, HOMA-IR >3.0). Mean blood pressure and type and number of antihypertensive medications did not differ between the groups. Compared with IS patients, IR patients were younger, had a higher BMI, higher triglycerides, and lower HDL, but there was substantial overlap of these risk factors between the groups. More IR than IS patients developed an impaired fasting glucose after 1 year (48% v 11%, P < .001). After 3 years of follow-up, 10% of the IR group and none from the IS group were confirmed as having type 2 diabetes mellitus.

CONCLUSIONS

In this study, insulin resistance was common (20%) and could not be reliably diagnosed using conventional risk factors. One-half of the IR patients developed an impaired fasting glucose by 1 year, and, of these individuals, 20% were confirmed as having type 2 diabetes mellitus by 3 years.

Altered tropomyosin expression in essential hypertension

Abnormal erythrocyte sodium-lithium countertransport is common in a subgroup of patients with essential hypertension and a strong family history of hypertension and cardiovascular disease. We have previously shown that the abnormality in sodium-lithium countertransport is associated with tropomyosin, a cytoskeletal protein required to stabilize actin filament formation. Leukocyte trafficking events, which depend on cytoskeletal reorganization, are also altered in patients with essential hypertension with abnormal sodium-lithium countertransport. The aim of this study was to determine whether there is an abnormality in isoforms of tropomyosin that are common to erythrocytes and leukocytes. Analysis of reticulocyte RNA by reverse transcription (RT) and polymerase chain reaction (PCR) showed expression of TPMN and TPM5b isoforms of tropomyosin. No other isoforms were expressed. These isoforms were also detected in RNA from leukocytes. In patients with essential hypertension with abnormal erythrocyte sodium-lithium countertransport compared with normal control subjects, there was a higher TPMN/TPM5b ratio of protein in erythrocytes (median 3.8 [range 1.8 to 6.6] versus 2.9 [1.9 to 4.0], P<0.001) and of RNA in leukocytes (3.7 [1.7 to 8.2] versus 2.6 [1.2 to 4.3], P<0.01). Furthermore, the protein ratio of TPMN/TPM5b in erythrocytes showed significant correlation with the V(max)/K(m) ratio of sodium-lithium countertransport across the patient groups (r=-0.42; P<0.01). Therefore, altered tropomyosin expression may be the underlying abnormality associated with blood cell membrane changes in essential hypertension and implicates the cytoskeleton in the pathogenesis of the disease in a major subgroup of patients.